第1章 ECMAScript 6简介

ECMAScript 6（以下简称ES6）是JavaScript语言的下一代标准，已于2015年6月正式发布。它的目标是使JavaScript语言可以用于编写复杂的大型应用程序，成为企业级开发语言。

1.1 ECMAScript 和 JavaScript 的关系

ECMAScript 和 JavaScript 的关系是，前者是后者的规格，后者是前者的一种实现（另外的 ECMAScript 方言还有 JScript 和 ActionScr）。

1.2 ES6 与 ECMAScript 2015 的关系

ES6 既是一个历史名词，也是一个泛指，含义是5.1版本以后的 JavaScript 的下一代标准，涵盖了ES2015、ES2016、ES2017等，而ES2015则是正式名称，特指当年发布的正式版本的语言标准。

1.3 语法提案的批准流程

一种新的语法从提案到变成正式标准，需要经历五个阶段。每个阶段的变动都要由 TC39 委员会批准。

Stage 0：Strawman（展示阶段）

Stage 1：Proposal（征求意见阶段）

Stage 2：Draft（草案阶段）

Stage 3：Candidate（候选阶段）

Stage 4：Finished（定案阶段）

1.4 ECMAScript的历史

【评】没有重点，省略。

1.5 部署进度

关于各大浏览器最新版本对于ES6的支持，可以参阅 kangax.github.io/es5-compat-table/es6/。

随着时间的推移，支持度已经越来越高，超过90%的ES6语法特性都实现了。

Node 是 JavaScript 语言的服务器运行环境（runtime），它对ES6的支持度更高。除了那些默认打开的功能，还有一些语法功能也已经实现了，但是默认没有打开。使用如下命令，可以查看 Node 中已经实现的ES6特性。

 node --v8-options | grep harmony

输入这条命令，结果显示的是：

 Microsoft Windows [版本 6.1.7601]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。
 
C:\Users\Administrator>node --v8-options | grep harmony
'grep' 不是内部或外部命令，也不是可运行的程序
或批处理文件。
 
C:\Users\Administrator>

所以，我改成输入以下这条命令：

 node --v8-options

是可以成功显示的：

         type: bool  default: false
  --trace-compiler-dispatcher (trace compiler dispatcher activity)
        type: bool  default: false
  --cpu-profiler-sampling-interval (CPU profiler sampling interval in microsecon
ds)
        type: int  default: 1000
  --trace-side-effect-free-debug-evaluate (print debug messages for side-effect-
free debug-evaluate for testing)
        type: bool  default: false
  --hard-abort (abort by crashing)
        type: bool  default: true
  --expose-inspector-scripts (expose injected-script-source.js for debugging)
        type: bool  default: false
  --stack-size (default size of stack region v8 is allowed to use (in kBytes))
        type: int  default: 984
  --max-stack-trace-source-length (maximum length of function source code printe
d in a stack trace.)
        type: int  default: 300
  --clear-exceptions-on-js-entry (clear pending exceptions when entering JavaScr
ipt)
        type: bool  default: false
  --histogram-interval (time interval in ms for aggregating memory histograms)
        type: int  default: 600000
  --heap-profiler-trace-objects (Dump heap object allocations/movements/size_upd
ates)
        type: bool  default: false
  --heap-profiler-use-embedder-graph (Use the new EmbedderGraph API to get embed
der nodes)
        type: bool  default: true
  --heap-snapshot-string-limit (truncate strings to this length in the heap snap
shot)
        type: int  default: 1024
  --sampling-heap-profiler-suppress-randomness (Use constant sample intervals to
 eliminate test flakiness)
        type: bool  default: false
  --use-idle-notification (Use idle notification to reduce memory footprint.)
        type: bool  default: true
  --trace-ic (trace inline cache state transitions for tools/ic-processor)
        type: bool  default: false
  --modify-field-representation-inplace (enable in-place field representation up
dates)
        type: bool  default: true
  --max-polymorphic-map-count (maximum number of maps to track in POLYMORPHIC st
ate)
        type: int  default: 4
  --native-code-counters (generate extra code for manipulating stats counters)
        type: bool  default: false
  --thin-strings (Enable ThinString support)
        type: bool  default: true
  --trace-prototype-users (Trace updates to prototype user tracking)
        type: bool  default: false
  --use-verbose-printer (allows verbose printing)
        type: bool  default: true
  --trace-for-in-enumerate (Trace for-in enumerate slow-paths)
        type: bool  default: false
  --trace-maps (trace map creation)
        type: bool  default: false
  --trace-maps-details (also log map details)
        type: bool  default: true
  --allow-natives-syntax (allow natives syntax)
        type: bool  default: false
  --parse-only (only parse the sources)
        type: bool  default: false
  --trace-sim (Trace simulator execution)
        type: bool  default: false
  --debug-sim (Enable debugging the simulator)
        type: bool  default: false
  --check-icache (Check icache flushes in ARM and MIPS simulator)
        type: bool  default: false
  --stop-sim-at (Simulator stop after x number of instructions)
        type: int  default: 0
  --sim-stack-alignment (Stack alingment in bytes in simulator (4 or 8, 8 is def
ault))
        type: int  default: 8
  --sim-stack-size (Stack size of the ARM64, MIPS64 and PPC64 simulator in kByte
s (default is 2 MB))
        type: int  default: 2048
  --log-colour (When logging, try to use coloured output.)
        type: bool  default: false
  --ignore-asm-unimplemented-break (Don't break for ASM_UNIMPLEMENTED_BREAK macr
os.)
        type: bool  default: false
  --trace-sim-messages (Trace simulator debug messages. Implied by --trace-sim.)
 
        type: bool  default: false
  --async-stack-traces (include async stack traces in Error.stack)
        type: bool  default: true
  --stack-trace-on-illegal (print stack trace when an illegal exception is throw
n)
        type: bool  default: false
  --abort-on-uncaught-exception (abort program (dump core) when an uncaught exce
ption is thrown)
        type: bool  default: false
  --correctness-fuzzer-suppressions (Suppress certain unspecified behaviors to e
ase correctness fuzzing: Abort program when the stack overflows or a string exce
eds maximum length (as opposed to throwing RangeError). Use a fixed suppression
string for error messages.)
        type: bool  default: false
  --randomize-hashes (randomize hashes to avoid predictable hash collisions (wit
h snapshots this option cannot override the baked-in seed))
        type: bool  default: true
  --rehash-snapshot (rehash strings from the snapshot to override the baked-in s
eed)
        type: bool  default: true
  --hash-seed (Fixed seed to use to hash property keys (0 means random)(with sna
pshots this option cannot override the baked-in seed))
        type: uint64  default: 0
  --random-seed (Default seed for initializing random generator (0, the default,
 means to use system random).)
        type: int  default: 0
  --fuzzer-random-seed (Default seed for initializing fuzzer random generator (0
, the default, means to use v8's random number generator seed).)
        type: int  default: 0
  --trace-rail (trace RAIL mode)
        type: bool  default: false
  --print-all-exceptions (print exception object and stack trace on each thrown
exception)
        type: bool  default: false
  --detailed-error-stack-trace (includes arguments for each function call in the
 error stack frames array)
        type: bool  default: false
  --runtime-call-stats (report runtime call counts and times)
        type: bool  default: false
  --profile-deserialization (Print the time it takes to deserialize the snapshot
.)
        type: bool  default: false
  --serialization-statistics (Collect statistics on serialized objects.)
        type: bool  default: false
  --serialization-chunk-size (Custom size for serialization chunks)
        type: uint  default: 4096
  --regexp-optimization (generate optimized regexp code)
        type: bool  default: true
  --regexp-mode-modifiers (enable inline flags in regexp.)
        type: bool  default: false
  --regexp-interpret-all (interpret all regexp code)
        type: bool  default: false
  --regexp-tier-up (enable regexp interpreter and tier up to the compiler)
        type: bool  default: false
  --testing-bool-flag (testing_bool_flag)
        type: bool  default: true
  --testing-maybe-bool-flag (testing_maybe_bool_flag)
        type: maybe_bool  default: unset
  --testing-int-flag (testing_int_flag)
        type: int  default: 13
  --testing-float-flag (float-flag)
        type: float  default: 2.5
  --testing-string-flag (string-flag)
        type: string  default: Hello, world!
  --testing-prng-seed (Seed used for threading test randomness)
        type: int  default: 42
  --testing-d8-test-runner (test runner turns on this flag to enable a check tha
t the funciton was prepared for optimization before marking it for optimization)
        type: bool  default: false
  --embedded-src (Path for the generated embedded data file. (mksnapshot only))
        type: string  default: nullptr
  --embedded-variant (Label to disambiguate symbols in embedded data file. (mksn
apshot only))
        type: string  default: nullptr
  --startup-src (Write V8 startup as C++ src. (mksnapshot only))
        type: string  default: nullptr
  --startup-blob (Write V8 startup blob file. (mksnapshot only))
        type: string  default: nullptr
  --target-arch (The mksnapshot target arch. (mksnapshot only))
        type: string  default: nullptr
  --target-os (The mksnapshot target os. (mksnapshot only))
        type: string  default: nullptr
  --minor-mc-parallel-marking (use parallel marking for the young generation)
        type: bool  default: true
  --trace-minor-mc-parallel-marking (trace parallel marking for the young genera
tion)
        type: bool  default: false
  --minor-mc (perform young generation mark compact GCs)
        type: bool  default: false
  --help (Print usage message, including flags, on console)
        type: bool  default: true
  --dump-counters (Dump counters on exit)
        type: bool  default: false
  --dump-counters-nvp (Dump counters as name-value pairs on exit)
        type: bool  default: false
  --use-external-strings (Use external strings for source code)
        type: bool  default: false
  --map-counters (Map counters to a file)
        type: string  default:
  --mock-arraybuffer-allocator (Use a mock ArrayBuffer allocator for testing.)
        type: bool  default: false
  --mock-arraybuffer-allocator-limit (Memory limit for mock ArrayBuffer allocato
r used to simulate OOM for testing.)
        type: size_t  default: 0
  --log (Minimal logging (no API, code, GC, suspect, or handles samples).)
        type: bool  default: false
  --log-all (Log all events to the log file.)
        type: bool  default: false
  --log-api (Log API events to the log file.)
        type: bool  default: false
  --log-code (Log code events to the log file without profiling.)
        type: bool  default: false
  --log-handles (Log global handle events.)
        type: bool  default: false
  --log-suspect (Log suspect operations.)
        type: bool  default: false
  --log-source-code (Log source code.)
        type: bool  default: false
  --log-function-events (Log function events (parse, compile, execute) separatel
y.)
        type: bool  default: false
  --prof (Log statistical profiling information (implies --log-code).)
        type: bool  default: false
  --detailed-line-info (Always generate detailed line information for CPU profil
ing.)
        type: bool  default: false
  --prof-sampling-interval (Interval for --prof samples (in microseconds).)
        type: int  default: 1000
  --prof-cpp (Like --prof, but ignore generated code.)
        type: bool  default: false
  --prof-browser-mode (Used with --prof, turns on browser-compatible mode for pr
ofiling.)
        type: bool  default: true
  --logfile (Specify the name of the log file.)
        type: string  default: v8.log
  --logfile-per-isolate (Separate log files for each isolate.)
        type: bool  default: true
  --ll-prof (Enable low-level linux profiler.)
        type: bool  default: false
  --perf-basic-prof (Enable perf linux profiler (basic support).)
        type: bool  default: false
  --perf-basic-prof-only-functions (Only report function code ranges to perf (i.
e. no stubs).)
        type: bool  default: false
  --perf-prof (Enable perf linux profiler (experimental annotate support).)
        type: bool  default: false
  --perf-prof-annotate-wasm (Used with --perf-prof, load wasm source map and pro
vide annotate support (experimental).)
        type: bool  default: false
  --perf-prof-unwinding-info (Enable unwinding info for perf linux profiler (exp
erimental).)
        type: bool  default: false
  --gc-fake-mmap (Specify the name of the file for fake gc mmap used in ll_prof)
        type: string  default: /tmp/__v8_gc__
  --log-internal-timer-events (Time internal events.)
        type: bool  default: false
  --log-instruction-stats (Log AArch64 instruction statistics.)
        type: bool  default: false
  --log-instruction-file (AArch64 instruction statistics log file.)
        type: string  default: arm64_inst.csv
  --log-instruction-period (AArch64 instruction statistics logging period.)
        type: int  default: 4194304
  --redirect-code-traces (output deopt information and disassembly into file cod
e-<pid>-<isolate id>.asm)
        type: bool  default: false
  --redirect-code-traces-to (output deopt information and disassembly into the g
iven file)
        type: string  default: nullptr
  --print-opt-source (print source code of optimized and inlined functions)
        type: bool  default: false
  --win64-unwinding-info (Enable unwinding info for Windows/x64)
        type: bool  default: true
  --interpreted-frames-native-stack (Show interpreted frames on the native stack
 (useful for external profilers).)
        type: bool  default: false
  --trace-elements-transitions (trace elements transitions)
        type: bool  default: false
  --trace-creation-allocation-sites (trace the creation of allocation sites)
        type: bool  default: false
  --print-code (print generated code)
        type: bool  default: false
  --print-opt-code (print optimized code)
        type: bool  default: false
  --print-opt-code-filter (filter for printing optimized code)
        type: string  default: *
  --print-code-verbose (print more information for code)
        type: bool  default: false
  --print-builtin-code (print generated code for builtins)
        type: bool  default: false
  --print-builtin-code-filter (filter for printing builtin code)
        type: string  default: *
  --print-regexp-code (print generated regexp code)
        type: bool  default: false
  --print-regexp-bytecode (print generated regexp bytecode)
        type: bool  default: false
  --print-builtin-size (print code size for builtins)
        type: bool  default: false
  --sodium (print generated code output suitable for use with the Sodium code vi
ewer)
        type: bool  default: false
  --print-all-code (enable all flags related to printing code)
        type: bool  default: false
  --predictable (enable predictable mode)
        type: bool  default: false
  --predictable-gc-schedule (Predictable garbage collection schedule. Fixes heap
 growing, idle, and memory reducing behavior.)
        type: bool  default: false
  --single-threaded (disable the use of background tasks)
        type: bool  default: false
  --single-threaded-gc (disable the use of background gc tasks)
        type: bool  default: false
 
C:\Users\Administrator>

执行以上命令，输出结果会因为版本的不同而有所不同。

笔者写了一个ES-Checker（ github.com/ruanyf/es-checker ）模块，用来检查各种运行环境对ES6的支持情况。

访问 ruanyf.github.io/es-checker 即可查看所用浏览器对ES6的支持程度。

运行下面的命令，可以查看本机对ES6的支持程度。

 Microsoft Windows [版本 6.1.7601]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。
 
C:\Users\Administrator>npm install -g es-checker
F:\Program Files\nodejs\es-checker -> F:\Program Files\nodejs\node_modules\es-ch
ecker\bin\check.js
+ es-checker@1.4.2
added 13 packages from 8 contributors in 10.119s
 
C:\Users\Administrator>es-checker
 
ECMAScript 6 Feature Detection (v1.4.2)
 
Variables
  √ let and const
  √ TDZ error for too-early access of let or const declarations
  √ Redefinition of const declarations not allowed
  √ destructuring assignments/declarations for arrays and objects
  √ ... operator
 
Data Types
  √ For...of loop
  √ Map, Set, WeakMap, WeakSet
  √ Symbol
  √ Symbols cannot be implicitly coerced
 
Number
  √ Octal (e.g. 0o1 ) and binary (e.g. 0b10 ) literal forms
  √ Old octal literal invalid now (e.g. 01 )
  √ Static functions added to Math (e.g. Math.hypot(), Math.acosh(), Math.imul(
) )
  √ Static functions added to Number (Number.isNaN(), Number.isInteger() )
 
String
  √ Methods added to String.prototype (String.prototype.includes(), String.prot
otype.repeat() )
  √ Unicode code-point escape form in string literals (e.g. \u{20BB7} )
  √ Unicode code-point escape form in identifier names (e.g. var \u{20BB7} = 42
; )
  √ Unicode code-point escape form in regular expressions (e.g. var regexp = /\
u{20BB7}/u; )
  √ y flag for sticky regular expressions (e.g. /b/y )
  √ Template String Literals
 
Function
  √ arrow function
  √ default function parameter values
  √ destructuring for function parameters
  √ Inferences for function name property for anonymous functions
  × Tail-call optimization for function calls and recursion
 
Array
  √ Methods added to Array.prototype ([].fill(), [].find(), [].findIndex(), [].
entries(), [].keys(), [].values() )
  √ Static functions added to Array (Array.from(), Array.of() )
  √ TypedArrays like Uint8Array, ArrayBuffer, Int8Array(), Int32Array(), Float6
4Array()
  √ Some Array methods (e.g. Int8Array.prototype.slice(), Int8Array.prototype.j
oin(), Int8Array.prototype.forEach() ) added to the TypedArray prototypes
  √ Some Array statics (e.g. Uint32Array.from(), Uint32Array.of() ) added to th
e TypedArray constructors
 
Object
  √ __proto__ in object literal definition sets [[Prototype]] link
  √ Static functions added to Object (Object.getOwnPropertySymbols(), Object.as
sign() )
  √ Object Literal Computed Property
  √ Object Literal Property Shorthands
  √ Proxies
  √ Reflect
 
Generator and Promise
  √ Generator function
  √ Promises
 
Class
  √ Class
  √ super allowed in object methods
  √ class ABC extends Array { .. }
 
Module
  × Module export command
  × Module import command
 
 
=========================================
Passes 39 feature Detections
Your runtime supports 92% of ECMAScript 6
=========================================

1.6 Babel转码器

Babel（ babeljs.io/ ）是一个广为使用的ES6转码器，可以将ES6代码转为ES5代码，从而在浏览器或其他环境执行。这意味着，可以用ES6的方式编写程序，而不用担心现有环境是否支持。

下面是一个例子。

上面的原始代码用了箭头函数，Babel 将其转为普通函数，这样就能在不支持箭头函数的 JavaScript 环境中执行了。

1.6.1 配置文件.babelrc

Babel的配置文件是.babelrc，存放在项目的根目录下。

使用 Babel 的第一步就是配置这个文件。

该文件用来设置转码规则和插件，基本格式如下。

 {
    "presets": [],
    "plugins": []
}

presets 字段设定转码规则，官方提供以下的规则集，可以根据需要进行安装。

 # 最新转码规则
$ npm install --save-dev babel-preset-latest

安装的结果：

 Microsoft Windows [版本 6.1.7601]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。
 
E:\HMV\Babel>npm install --save-dev babel-preset-latest
npm WARN deprecated babel-preset-latest@6.24.1: We're super 😸  excited that you
're trying to use ES2017+ syntax, but instead of making more yearly presets 😭 ,
 Babel now has a better preset that we recommend you use instead: npm install ba
bel-preset-env --save-dev. preset-env without options will compile ES2015+ down
to ES5 just like using all the presets together and thus is more future proof. I
t also allows you to target specific browsers so that Babel can do less work and
 you can ship native ES2015+ to user 😎 ! We are also in the process of releasin
g v7, so please give http://babeljs.io/blog/2017/09/12/planning-for-7.0 a read a
nd help test it out in beta! Thanks so much for using Babel 🙏, please give us a
 follow on Twitter @babeljs for news on Babel, join slack.babeljs.io for discuss
ion/development and help support the project at opencollective.com/babel
npm WARN deprecated babel-preset-es2015@6.24.1: 🙌  Thanks for using Babel: we r
ecommend using babel-preset-env now: please read https://babeljs.io/env to updat
e!
npm WARN deprecated babel-preset-es2016@6.24.1: 🙌  Thanks for using Babel: we r
ecommend using babel-preset-env now: please read https://babeljs.io/env to updat
e!
npm WARN deprecated babel-preset-es2017@6.24.1: 🙌  Thanks for using Babel: we r
ecommend using babel-preset-env now: please read https://babeljs.io/env to updat
e!
npm WARN deprecated core-js@2.6.12: core-js@<3.4 is no longer maintained and not
 recommended for usage due to the number of issues. Because of the V8 engine whi
ms, feature detection in old core-js versions could cause a slowdown up to 100x
even if nothing is polyfilled. Please, upgrade your dependencies to the actual v
ersion of core-js.
> core-js@2.6.12 postinstall E:\HMV\node_modules\core-js
> node -e "try{require('./postinstall')}catch(e){}"
 
Thank you for using core-js ( https://github.com/zloirock/core-js ) for polyfill
ing JavaScript standard library!
 
The project needs your help! Please consider supporting of core-js on Open Colle
ctive or Patreon:
> https://opencollective.com/core-js
> https://www.patreon.com/zloirock
 
Also, the author of core-js ( https://github.com/zloirock ) is looking for a goo
d job -)
 
npm notice created a lockfile as package-lock.json. You should commit this file.
 
npm WARN HMV No description
npm WARN HMV No repository field.
npm WARN HMV No license field.
 
+ babel-preset-latest@6.24.1
added 78 packages from 14 contributors and removed 19 packages in 18.695s
 
E:\HMV\Babel>

 # react 转码规则
$ npm install --save-dev babel-preset-react

安装的结果：

 E:\HMV\Babel>npm install --save-dev babel-preset-react
npm WARN HMV No description
npm WARN HMV No repository field.
npm WARN HMV No license field.
 
+ babel-preset-react@6.24.1
added 10 packages from 2 contributors and removed 1 package in 5.248s

 # 不同阶段语法提案的转码规则（共有4个阶段），选装一个
$ npm install --save-dev babel-preset-stage-0
$ npm install --save-dev babel-preset-stage-1
$ npm install --save-dev babel-preset-stage-2
$ npm install --save-dev babel-preset-stage-3

安装的结果：

 Microsoft Windows [版本 6.1.7601]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。
 
E:\HMV\Babel>npm install --save-dev babel-preset-stage-2
npm WARN HMV No description
npm WARN HMV No repository field.
npm WARN HMV No license field.
 
+ babel-preset-stage-2@6.24.1
added 13 packages from 1 contributor and removed 1 package in 9.291s
 
E:\HMV\Babel>

然后，将这些规则加入.babelrc中。

 {
    "presets": [
        "latest",
        "react",
        "stage-2"
    ],
    "plugins": []
}

1.6.2 命令行转码babel-cli

Babel 提供 babel-cli 工具，用于命令行转码。

它的安装命令如下。

 $ npm install --global babel-cli

安装结果如下：

 Microsoft Windows [版本 6.1.7601]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。
 
E:\HMV\Babel>npm install --global babel-cli
npm WARN deprecated chokidar@1.7.0: Chokidar 2 will break on node v14+. Upgrade
to chokidar 3 with 15x less dependencies.
npm WARN deprecated core-js@2.6.12: core-js@<3.4 is no longer maintained and not
 recommended for usage due to the number of issues. Because of the V8 engine whi
ms, feature detection in old core-js versions could cause a slowdown up to 100x
even if nothing is polyfilled. Please, upgrade your dependencies to the actual v
ersion of core-js.
npm WARN deprecated fsevents@1.2.13: fsevents 1 will break on node v14+ and coul
d be using insecure binaries. Upgrade to fsevents 2.
npm WARN deprecated source-map-resolve@0.5.3: See https://github.com/lydell/sour
ce-map-resolve#deprecated
npm WARN deprecated source-map-url@0.4.1: See https://github.com/lydell/source-m
ap-url#deprecated
npm WARN deprecated urix@0.1.0: Please see https://github.com/lydell/urix#deprec
ated
npm WARN deprecated resolve-url@0.2.1: https://github.com/lydell/resolve-url#dep
recated
F:\Program Files\nodejs\babel-node -> F:\Program Files\nodejs\node_modules\babel
-cli\bin\babel-node.js
F:\Program Files\nodejs\babel-doctor -> F:\Program Files\nodejs\node_modules\bab
el-cli\bin\babel-doctor.js
F:\Program Files\nodejs\babel -> F:\Program Files\nodejs\node_modules\babel-cli\
bin\babel.js
F:\Program Files\nodejs\babel-external-helpers -> F:\Program Files\nodejs\node_m
odules\babel-cli\bin\babel-external-helpers.js
> core-js@2.6.12 postinstall F:\Program Files\nodejs\node_modules\babel-cli\node
_modules\core-js
> node -e "try{require('./postinstall')}catch(e){}"
 
Thank you for using core-js ( https://github.com/zloirock/core-js ) for polyfill
ing JavaScript standard library!
 
The project needs your help! Please consider supporting of core-js on Open Colle
ctive or Patreon:
> https://opencollective.com/core-js
> https://www.patreon.com/zloirock
 
Also, the author of core-js ( https://github.com/zloirock ) is looking for a goo
d job -)
 
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@^1.0.0 (node_modules\ba
bel-cli\node_modules\chokidar\node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@
1.2.13: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"
})
 
+ babel-cli@6.26.0
added 234 packages from 119 contributors in 61.661s
 
E:\HMV\Babel>

babel-cli 基本用法

基本用法如下。

转码结果输出到标准输出

 # 转码结果输出到标准输出
$ babel hzh.js

直接使用源文件名字进行转码：

 // hzh.js
var input = [1, 2, 3];
input.map(item => item + 1);

 Microsoft Windows [版本 6.1.7601]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。
 
E:\HMV\Babel>babel hzh.js
"use strict";
 
var input = [1, 2, 3];
input.map(function (item) {
  return item + 1;
});
 
 
E:\HMV\Babel>

转码结果写入一个文件

 # 转码结果写入一个文件
# --out-file 或 -o 参数指定输出文件
$ babel hzh.js --out-file huangzihan.js
# 或者
$ babel hzh.js --o huangzihan.js

下面是hzh.js和huangzihan.js两个文件的代码：

 // hzh.js
 
var input = [1, 2, 3];
input.map(item => item + 1);
 
// huangzihan.js
 
"use strict";
 
var input = [1, 2, 3];
input.map(function (item) {
  return item + 1;
});

终端的输入和输出是这样的：

 Microsoft Windows [版本 6.1.7601]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。
 
E:\HMV\Babel>babel hzh.js -o huangzihan.js
E:\HMV\Babel>

整个目录转码

 # 整个目录转码
# --out-dir 或 -d 参数指定输出目录
$ babel hzh1 --out-dir hzh2
# 或者
$ babel hzh1 -d hzh2

下面是hzh1目录下hzh11.js和hzh12.js文件的代码：

 // hzh11.js
 
var hzh11 = [1, 2, 3];
hzh11.map(item => item + 1);
 
// hzh12.js
 
var hzh12 = [1, 2, 3];
hzh12.map(item => item + 1);

转码之前项目目录的结构：

终端的输入和输出：

 Microsoft Windows [版本 6.1.7601]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。
 
E:\HMV\Babel>babel hzh1 -d hzh2
hzh1\hzh11.js -> hzh2\hzh11.js
hzh1\hzh12.js -> hzh2\hzh12.js
E:\HMV\Babel>

转码之后项目目录的结构：

生成 source map 文件

 # -s 参数 生成source map 文件
$ babel hzh1 -d hzh2 -s

转码之前项目目录的结构：

转码之前hzh1目录下各个文件的代码：

 // hzh1.js
 
var hzh11 = [1, 2, 3];
hzh11.map(item => item + 1);
 
// hzh2.js
 
var hzh12 = [1, 2, 3];
hzh12.map(item => item + 1);

终端的输入与输出：

 Microsoft Windows [版本 6.1.7601]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。
 
E:\HMV\Babel>babel hzh1 -d hzh2 -s
hzh1\hzh11.js -> hzh2\hzh11.js
hzh1\hzh12.js -> hzh2\hzh12.js
E:\HMV\Babel>

转码之后项目目录的结构：

转码之后hzh2目录下各个文件的代码：

 // hzh11.js
"use strict";
 
var hzh11 = [1, 2, 3];
hzh11.map(function (item) {
  return item + 1;
});
//# sourceMappingURL=hzh11.js.map
 
// hzh11.js.map
 
{"version":3,"sources":["../hzh1/hzh11.js"],"names":["hzh11","map","item"],"mappings":";;AAAA,IAAIA,QAAQ,CAAC,CAAD,EAAI,CAAJ,EAAO,CAAP,CAAZ;AACAA,MAAMC,GAAN,CAAU;AAAA,SAAQC,OAAO,CAAf;AAAA,CAAV","file":"hzh11.js","sourcesContent":["var hzh11 = [1, 2, 3];\r\nhzh11.map(item => item + 1);"]}
 
// hzh12.js
"use strict";
 
var hzh12 = [1, 2, 3];
hzh12.map(function (item) {
  return item + 1;
});
//# sourceMappingURL=hzh12.js.map
 
// hzh12.js.map
 
{"version":3,"sources":["../hzh1/hzh12.js"],"names":["hzh12","map","item"],"mappings":";;AAAA,IAAIA,QAAQ,CAAC,CAAD,EAAI,CAAJ,EAAO,CAAP,CAAZ;AACAA,MAAMC,GAAN,CAAU;AAAA,SAAQC,OAAO,CAAf;AAAA,CAAV","file":"hzh12.js","sourcesContent":["var hzh12 = [1, 2, 3];\r\nhzh12.map(item => item + 1);"]}

在项目中运行 Babel

上面的代码是在全局环境下进行 Babel 转码的。这意味着，如果项目要运行，全局环境中必须有 Babel，也就是说项目产生了对环境的依赖。另一方面，这样做也无法支持不同项目使用不同版本的Babel。

一个解决办法是将 babel-cli 安装在项目之中，代码如下。

什么项目需要再回来看下这个，先摘抄下来。

 # 安装
$ npm install --save-dev babel-cli

然后，改写package.json。

 {
  // ...
 
  "devDependencies": {
       "babel-cli": "^6.0.0"
   },
   "scripts": {
       "build": "babel src -d lib"
   },
}

转码的时候需要执行以下命令。

 $ npm run build

1.6.3 babel-node

babel-cli 工具自带一个babel-node命令，提供一个支持 ES6 的 REPL 环境。它支持 Node 的 REPL 环境的所有功能，而且可以直接运行 ES6 代码。

babel-node 不用单独安装，而是随 babel-cli 一起安装。执行 babel-node 可以进入 REPL 环境。

 $ babel-node
> (x => x * 2)(1)
2

模仿上面的代码，在终端上输入和输出的结果：

 Microsoft Windows [版本 6.1.7601]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。
 
E:\HMV\Babel>babel-node
> (hzh => hzh * 3)(2)
6
>

babel-node 命令可以直接运行 ES6 脚本。将上面的代码放入脚本文件 es6.js，然后直接运行。

 $ babel-node es6.js
2

根据上面的描述，我在项目目录下新建了一个hzh.js文件，一开始直接将上面的套进去发现是没有输出的，经过思考，修改为下面的代码，就有了输出，下面分别给出hzh.js和终端的代码：

 // hzh.js
 
console.log((hzh => hzh * 4)(3));

 Microsoft Windows [版本 6.1.7601]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。
 
E:\HMV\Babel>babel-node hzh.js
12

babel-node 也可以安装在项目中。

 $ npm install --save-dev babel-cli

安装的结果如下：

 Microsoft Windows [版本 6.1.7601]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。
 
E:\HMV\Babel>npm install --save-dev babel-cli
npm WARN deprecated chokidar@1.7.0: Chokidar 2 will break on node v14+. Upgrade to chokidar 3 with 15x less dependencies.
npm WARN deprecated fsevents@1.2.13: fsevents 1 will break on node v14+ and could be using insecure binaries. Upgrade to fsevents 2.
npm WARN deprecated source-map-resolve@0.5.3: See https://github.com/lydell/source-map-resolve#deprecated
npm WARN deprecated urix@0.1.0: Please see https://github.com/lydell/urix#deprecated
npm WARN deprecated resolve-url@0.2.1: https://github.com/lydell/resolve-url#deprecated
npm WARN deprecated source-map-url@0.4.1: See https://github.com/lydell/source-map-url#deprecated
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@^1.0.0 (node_modules\chokidar\node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.13: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})
npm WARN HMV No description
npm WARN HMV No repository field.
npm WARN HMV No license field.
 
+ babel-cli@6.26.0
added 211 packages from 122 contributors and removed 1 package in 81.97s
 
2 packages are looking for funding
  run `npm fund` for details
 
 
E:\HMV\Babel>

然后，改写 package.json。

 {
    "script": {
        "script-name": "babel-node script.js"
    }
}

在以上代码中，使用 babel-node 替代 node，这样 script.js 本身就不用进行任何转码处理了

这句不太明白是啥意思？

1.6.4 babel-register

1.6.5 babel-core

1.6.6 babel-polyfill

1.6.7 浏览器环境

1.6.8 在线转换

1.6.9 与其他工具的配合

1.7 Traceur转码器

1.7.1 直接插入网页

1.7.2 在线转换

1.7.3 命令行转换

1.7.4 Node环境的用法

posted @ 2022-05-10 19:19 黄子涵阅读(169) 评论(0) 编辑收藏举报

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2025年3月

日

一

二

三

四

五

六

黄子涵

第1章 ECMAScript 6简介

1.1 ECMAScript 和 JavaScript 的关系

1.2 ES6 与 ECMAScript 2015 的关系

1.3 语法提案的批准流程

1.4 ECMAScript的历史

1.5 部署进度

1.6 Babel转码器

1.6.1 配置文件.babelrc

1.6.2 命令行转码babel-cli

babel-cli 基本用法

转码结果输出到标准输出

转码结果写入一个文件

整个目录转码

生成 source map 文件

在项目中运行 Babel

1.6.3 babel-node

1.6.4 babel-register

1.6.5 babel-core

1.6.6 babel-polyfill

1.6.7 浏览器环境

1.6.8 在线转换

1.6.9 与其他工具的配合

1.7 Traceur转码器

1.7.1 直接插入网页

1.7.2 在线转换

1.7.3 命令行转换

1.7.4 Node环境的用法

公告

搜索

常用链接

我的标签

随笔分类

随笔档案

阅读排行榜

	Microsoft Windows [版本 6.1.7601]
	版权所有 (c) 2009 Microsoft Corporation。保留所有权利。

	C:\Users\Administrator>node --v8-options \| grep harmony
	'grep' 不是内部或外部命令，也不是可运行的程序
	或批处理文件。

	C:\Users\Administrator>

	type: bool default: false
	--trace-compiler-dispatcher (trace compiler dispatcher activity)
	type: bool default: false
	--cpu-profiler-sampling-interval (CPU profiler sampling interval in microsecon
	ds)
	type: int default: 1000
	--trace-side-effect-free-debug-evaluate (print debug messages for side-effect-
	free debug-evaluate for testing)
	type: bool default: false
	--hard-abort (abort by crashing)
	type: bool default: true
	--expose-inspector-scripts (expose injected-script-source.js for debugging)
	type: bool default: false
	--stack-size (default size of stack region v8 is allowed to use (in kBytes))
	type: int default: 984
	--max-stack-trace-source-length (maximum length of function source code printe
	d in a stack trace.)
	type: int default: 300
	--clear-exceptions-on-js-entry (clear pending exceptions when entering JavaScr
	ipt)
	type: bool default: false
	--histogram-interval (time interval in ms for aggregating memory histograms)
	type: int default: 600000
	--heap-profiler-trace-objects (Dump heap object allocations/movements/size_upd
	ates)
	type: bool default: false
	--heap-profiler-use-embedder-graph (Use the new EmbedderGraph API to get embed
	der nodes)
	type: bool default: true
	--heap-snapshot-string-limit (truncate strings to this length in the heap snap
	shot)
	type: int default: 1024
	--sampling-heap-profiler-suppress-randomness (Use constant sample intervals to
	eliminate test flakiness)
	type: bool default: false
	--use-idle-notification (Use idle notification to reduce memory footprint.)
	type: bool default: true
	--trace-ic (trace inline cache state transitions for tools/ic-processor)
	type: bool default: false
	--modify-field-representation-inplace (enable in-place field representation up
	dates)
	type: bool default: true
	--max-polymorphic-map-count (maximum number of maps to track in POLYMORPHIC st
	ate)
	type: int default: 4
	--native-code-counters (generate extra code for manipulating stats counters)
	type: bool default: false
	--thin-strings (Enable ThinString support)
	type: bool default: true
	--trace-prototype-users (Trace updates to prototype user tracking)
	type: bool default: false
	--use-verbose-printer (allows verbose printing)
	type: bool default: true
	--trace-for-in-enumerate (Trace for-in enumerate slow-paths)
	type: bool default: false
	--trace-maps (trace map creation)
	type: bool default: false
	--trace-maps-details (also log map details)
	type: bool default: true
	--allow-natives-syntax (allow natives syntax)
	type: bool default: false
	--parse-only (only parse the sources)
	type: bool default: false
	--trace-sim (Trace simulator execution)
	type: bool default: false
	--debug-sim (Enable debugging the simulator)
	type: bool default: false
	--check-icache (Check icache flushes in ARM and MIPS simulator)
	type: bool default: false
	--stop-sim-at (Simulator stop after x number of instructions)
	type: int default: 0
	--sim-stack-alignment (Stack alingment in bytes in simulator (4 or 8, 8 is def
	ault))
	type: int default: 8
	--sim-stack-size (Stack size of the ARM64, MIPS64 and PPC64 simulator in kByte
	s (default is 2 MB))
	type: int default: 2048
	--log-colour (When logging, try to use coloured output.)
	type: bool default: false
	--ignore-asm-unimplemented-break (Don't break for ASM_UNIMPLEMENTED_BREAK macr
	os.)
	type: bool default: false
	--trace-sim-messages (Trace simulator debug messages. Implied by --trace-sim.)

	type: bool default: false
	--async-stack-traces (include async stack traces in Error.stack)
	type: bool default: true
	--stack-trace-on-illegal (print stack trace when an illegal exception is throw
	n)
	type: bool default: false
	--abort-on-uncaught-exception (abort program (dump core) when an uncaught exce
	ption is thrown)
	type: bool default: false
	--correctness-fuzzer-suppressions (Suppress certain unspecified behaviors to e
	ase correctness fuzzing: Abort program when the stack overflows or a string exce
	eds maximum length (as opposed to throwing RangeError). Use a fixed suppression
	string for error messages.)
	type: bool default: false
	--randomize-hashes (randomize hashes to avoid predictable hash collisions (wit
	h snapshots this option cannot override the baked-in seed))
	type: bool default: true
	--rehash-snapshot (rehash strings from the snapshot to override the baked-in s
	eed)
	type: bool default: true
	--hash-seed (Fixed seed to use to hash property keys (0 means random)(with sna
	pshots this option cannot override the baked-in seed))
	type: uint64 default: 0
	--random-seed (Default seed for initializing random generator (0, the default,
	means to use system random).)
	type: int default: 0
	--fuzzer-random-seed (Default seed for initializing fuzzer random generator (0
	, the default, means to use v8's random number generator seed).)
	type: int default: 0
	--trace-rail (trace RAIL mode)
	type: bool default: false
	--print-all-exceptions (print exception object and stack trace on each thrown
	exception)
	type: bool default: false
	--detailed-error-stack-trace (includes arguments for each function call in the
	error stack frames array)
	type: bool default: false
	--runtime-call-stats (report runtime call counts and times)
	type: bool default: false
	--profile-deserialization (Print the time it takes to deserialize the snapshot
	.)
	type: bool default: false
	--serialization-statistics (Collect statistics on serialized objects.)
	type: bool default: false
	--serialization-chunk-size (Custom size for serialization chunks)
	type: uint default: 4096
	--regexp-optimization (generate optimized regexp code)
	type: bool default: true
	--regexp-mode-modifiers (enable inline flags in regexp.)
	type: bool default: false
	--regexp-interpret-all (interpret all regexp code)
	type: bool default: false
	--regexp-tier-up (enable regexp interpreter and tier up to the compiler)
	type: bool default: false
	--testing-bool-flag (testing_bool_flag)
	type: bool default: true
	--testing-maybe-bool-flag (testing_maybe_bool_flag)
	type: maybe_bool default: unset
	--testing-int-flag (testing_int_flag)
	type: int default: 13
	--testing-float-flag (float-flag)
	type: float default: 2.5
	--testing-string-flag (string-flag)
	type: string default: Hello, world!
	--testing-prng-seed (Seed used for threading test randomness)
	type: int default: 42
	--testing-d8-test-runner (test runner turns on this flag to enable a check tha
	t the funciton was prepared for optimization before marking it for optimization)

	type: bool default: false
	--embedded-src (Path for the generated embedded data file. (mksnapshot only))
	type: string default: nullptr
	--embedded-variant (Label to disambiguate symbols in embedded data file. (mksn
	apshot only))
	type: string default: nullptr
	--startup-src (Write V8 startup as C++ src. (mksnapshot only))
	type: string default: nullptr
	--startup-blob (Write V8 startup blob file. (mksnapshot only))
	type: string default: nullptr
	--target-arch (The mksnapshot target arch. (mksnapshot only))
	type: string default: nullptr
	--target-os (The mksnapshot target os. (mksnapshot only))
	type: string default: nullptr
	--minor-mc-parallel-marking (use parallel marking for the young generation)
	type: bool default: true
	--trace-minor-mc-parallel-marking (trace parallel marking for the young genera
	tion)
	type: bool default: false
	--minor-mc (perform young generation mark compact GCs)
	type: bool default: false
	--help (Print usage message, including flags, on console)
	type: bool default: true
	--dump-counters (Dump counters on exit)
	type: bool default: false
	--dump-counters-nvp (Dump counters as name-value pairs on exit)
	type: bool default: false
	--use-external-strings (Use external strings for source code)
	type: bool default: false
	--map-counters (Map counters to a file)
	type: string default:
	--mock-arraybuffer-allocator (Use a mock ArrayBuffer allocator for testing.)
	type: bool default: false
	--mock-arraybuffer-allocator-limit (Memory limit for mock ArrayBuffer allocato
	r used to simulate OOM for testing.)
	type: size_t default: 0
	--log (Minimal logging (no API, code, GC, suspect, or handles samples).)
	type: bool default: false
	--log-all (Log all events to the log file.)
	type: bool default: false
	--log-api (Log API events to the log file.)
	type: bool default: false
	--log-code (Log code events to the log file without profiling.)
	type: bool default: false
	--log-handles (Log global handle events.)
	type: bool default: false
	--log-suspect (Log suspect operations.)
	type: bool default: false
	--log-source-code (Log source code.)
	type: bool default: false
	--log-function-events (Log function events (parse, compile, execute) separatel
	y.)
	type: bool default: false
	--prof (Log statistical profiling information (implies --log-code).)
	type: bool default: false
	--detailed-line-info (Always generate detailed line information for CPU profil
	ing.)
	type: bool default: false
	--prof-sampling-interval (Interval for --prof samples (in microseconds).)
	type: int default: 1000
	--prof-cpp (Like --prof, but ignore generated code.)
	type: bool default: false
	--prof-browser-mode (Used with --prof, turns on browser-compatible mode for pr
	ofiling.)
	type: bool default: true
	--logfile (Specify the name of the log file.)
	type: string default: v8.log
	--logfile-per-isolate (Separate log files for each isolate.)
	type: bool default: true
	--ll-prof (Enable low-level linux profiler.)
	type: bool default: false
	--perf-basic-prof (Enable perf linux profiler (basic support).)
	type: bool default: false
	--perf-basic-prof-only-functions (Only report function code ranges to perf (i.
	e. no stubs).)
	type: bool default: false
	--perf-prof (Enable perf linux profiler (experimental annotate support).)
	type: bool default: false
	--perf-prof-annotate-wasm (Used with --perf-prof, load wasm source map and pro
	vide annotate support (experimental).)
	type: bool default: false
	--perf-prof-unwinding-info (Enable unwinding info for perf linux profiler (exp
	erimental).)
	type: bool default: false
	--gc-fake-mmap (Specify the name of the file for fake gc mmap used in ll_prof)

	type: string default: /tmp/__v8_gc__
	--log-internal-timer-events (Time internal events.)
	type: bool default: false
	--log-instruction-stats (Log AArch64 instruction statistics.)
	type: bool default: false
	--log-instruction-file (AArch64 instruction statistics log file.)
	type: string default: arm64_inst.csv
	--log-instruction-period (AArch64 instruction statistics logging period.)
	type: int default: 4194304
	--redirect-code-traces (output deopt information and disassembly into file cod
	e-<pid>-<isolate id>.asm)
	type: bool default: false
	--redirect-code-traces-to (output deopt information and disassembly into the g
	iven file)
	type: string default: nullptr
	--print-opt-source (print source code of optimized and inlined functions)
	type: bool default: false
	--win64-unwinding-info (Enable unwinding info for Windows/x64)
	type: bool default: true
	--interpreted-frames-native-stack (Show interpreted frames on the native stack
	(useful for external profilers).)
	type: bool default: false
	--trace-elements-transitions (trace elements transitions)
	type: bool default: false
	--trace-creation-allocation-sites (trace the creation of allocation sites)
	type: bool default: false
	--print-code (print generated code)
	type: bool default: false
	--print-opt-code (print optimized code)
	type: bool default: false
	--print-opt-code-filter (filter for printing optimized code)
	type: string default: *
	--print-code-verbose (print more information for code)
	type: bool default: false
	--print-builtin-code (print generated code for builtins)
	type: bool default: false
	--print-builtin-code-filter (filter for printing builtin code)
	type: string default: *
	--print-regexp-code (print generated regexp code)
	type: bool default: false
	--print-regexp-bytecode (print generated regexp bytecode)
	type: bool default: false
	--print-builtin-size (print code size for builtins)
	type: bool default: false
	--sodium (print generated code output suitable for use with the Sodium code vi
	ewer)
	type: bool default: false
	--print-all-code (enable all flags related to printing code)
	type: bool default: false
	--predictable (enable predictable mode)
	type: bool default: false
	--predictable-gc-schedule (Predictable garbage collection schedule. Fixes heap
	growing, idle, and memory reducing behavior.)
	type: bool default: false
	--single-threaded (disable the use of background tasks)
	type: bool default: false
	--single-threaded-gc (disable the use of background gc tasks)
	type: bool default: false

	C:\Users\Administrator>

	Microsoft Windows [版本 6.1.7601]
	版权所有 (c) 2009 Microsoft Corporation。保留所有权利。

	C:\Users\Administrator>npm install -g es-checker
	F:\Program Files\nodejs\es-checker -> F:\Program Files\nodejs\node_modules\es-ch
	ecker\bin\check.js
	+ es-checker@1.4.2
	added 13 packages from 8 contributors in 10.119s

	C:\Users\Administrator>es-checker

	ECMAScript 6 Feature Detection (v1.4.2)

	Variables
	√ let and const
	√ TDZ error for too-early access of let or const declarations
	√ Redefinition of const declarations not allowed
	√ destructuring assignments/declarations for arrays and objects
	√ ... operator

	Data Types
	√ For...of loop
	√ Map, Set, WeakMap, WeakSet
	√ Symbol
	√ Symbols cannot be implicitly coerced

	Number
	√ Octal (e.g. 0o1 ) and binary (e.g. 0b10 ) literal forms
	√ Old octal literal invalid now (e.g. 01 )
	√ Static functions added to Math (e.g. Math.hypot(), Math.acosh(), Math.imul(
	) )
	√ Static functions added to Number (Number.isNaN(), Number.isInteger() )

	String
	√ Methods added to String.prototype (String.prototype.includes(), String.prot
	otype.repeat() )
	√ Unicode code-point escape form in string literals (e.g. \u{20BB7} )
	√ Unicode code-point escape form in identifier names (e.g. var \u{20BB7} = 42
	; )
	√ Unicode code-point escape form in regular expressions (e.g. var regexp = /\
	u{20BB7}/u; )
	√ y flag for sticky regular expressions (e.g. /b/y )
	√ Template String Literals

	Function
	√ arrow function
	√ default function parameter values
	√ destructuring for function parameters
	√ Inferences for function name property for anonymous functions
	× Tail-call optimization for function calls and recursion

	Array
	√ Methods added to Array.prototype ([].fill(), [].find(), [].findIndex(), [].
	entries(), [].keys(), [].values() )
	√ Static functions added to Array (Array.from(), Array.of() )
	√ TypedArrays like Uint8Array, ArrayBuffer, Int8Array(), Int32Array(), Float6
	4Array()
	√ Some Array methods (e.g. Int8Array.prototype.slice(), Int8Array.prototype.j
	oin(), Int8Array.prototype.forEach() ) added to the TypedArray prototypes
	√ Some Array statics (e.g. Uint32Array.from(), Uint32Array.of() ) added to th
	e TypedArray constructors

	Object
	√ __proto__ in object literal definition sets [[Prototype]] link
	√ Static functions added to Object (Object.getOwnPropertySymbols(), Object.as
	sign() )
	√ Object Literal Computed Property
	√ Object Literal Property Shorthands
	√ Proxies
	√ Reflect

	Generator and Promise
	√ Generator function
	√ Promises

	Class
	√ Class
	√ super allowed in object methods
	√ class ABC extends Array { .. }

	Module
	× Module export command
	× Module import command


	=========================================
	Passes 39 feature Detections
	Your runtime supports 92% of ECMAScript 6
	=========================================

	# 最新转码规则
	$ npm install --save-dev babel-preset-latest

	Microsoft Windows [版本 6.1.7601]
	版权所有 (c) 2009 Microsoft Corporation。保留所有权利。

	E:\HMV\Babel>npm install --save-dev babel-preset-latest
	npm WARN deprecated babel-preset-latest@6.24.1: We're super 😸 excited that you
	're trying to use ES2017+ syntax, but instead of making more yearly presets 😭 ,
	Babel now has a better preset that we recommend you use instead: npm install ba
	bel-preset-env --save-dev. preset-env without options will compile ES2015+ down
	to ES5 just like using all the presets together and thus is more future proof. I
	t also allows you to target specific browsers so that Babel can do less work and
	you can ship native ES2015+ to user 😎 ! We are also in the process of releasin
	g v7, so please give http://babeljs.io/blog/2017/09/12/planning-for-7.0 a read a
	nd help test it out in beta! Thanks so much for using Babel 🙏, please give us a
	follow on Twitter @babeljs for news on Babel, join slack.babeljs.io for discuss
	ion/development and help support the project at opencollective.com/babel
	npm WARN deprecated babel-preset-es2015@6.24.1: 🙌 Thanks for using Babel: we r
	ecommend using babel-preset-env now: please read https://babeljs.io/env to updat
	e!
	npm WARN deprecated babel-preset-es2016@6.24.1: 🙌 Thanks for using Babel: we r
	ecommend using babel-preset-env now: please read https://babeljs.io/env to updat
	e!
	npm WARN deprecated babel-preset-es2017@6.24.1: 🙌 Thanks for using Babel: we r
	ecommend using babel-preset-env now: please read https://babeljs.io/env to updat
	e!
	npm WARN deprecated core-js@2.6.12: core-js@<3.4 is no longer maintained and not
	recommended for usage due to the number of issues. Because of the V8 engine whi
	ms, feature detection in old core-js versions could cause a slowdown up to 100x
	even if nothing is polyfilled. Please, upgrade your dependencies to the actual v
	ersion of core-js.

	> core-js@2.6.12 postinstall E:\HMV\node_modules\core-js
	> node -e "try{require('./postinstall')}catch(e){}"

	Thank you for using core-js ( https://github.com/zloirock/core-js ) for polyfill
	ing JavaScript standard library!

	The project needs your help! Please consider supporting of core-js on Open Colle
	ctive or Patreon:
	> https://opencollective.com/core-js
	> https://www.patreon.com/zloirock

	Also, the author of core-js ( https://github.com/zloirock ) is looking for a goo
	d job -)

	npm notice created a lockfile as package-lock.json. You should commit this file.

	npm WARN HMV No description
	npm WARN HMV No repository field.
	npm WARN HMV No license field.

	+ babel-preset-latest@6.24.1
	added 78 packages from 14 contributors and removed 19 packages in 18.695s

	E:\HMV\Babel>

	# react 转码规则
	$ npm install --save-dev babel-preset-react

	# 不同阶段语法提案的转码规则（共有4个阶段），选装一个
	$ npm install --save-dev babel-preset-stage-0
	$ npm install --save-dev babel-preset-stage-1
	$ npm install --save-dev babel-preset-stage-2
	$ npm install --save-dev babel-preset-stage-3

	Microsoft Windows [版本 6.1.7601]
	版权所有 (c) 2009 Microsoft Corporation。保留所有权利。

	E:\HMV\Babel>npm install --global babel-cli
	npm WARN deprecated chokidar@1.7.0: Chokidar 2 will break on node v14+. Upgrade
	to chokidar 3 with 15x less dependencies.
	npm WARN deprecated core-js@2.6.12: core-js@<3.4 is no longer maintained and not
	recommended for usage due to the number of issues. Because of the V8 engine whi
	ms, feature detection in old core-js versions could cause a slowdown up to 100x
	even if nothing is polyfilled. Please, upgrade your dependencies to the actual v
	ersion of core-js.
	npm WARN deprecated fsevents@1.2.13: fsevents 1 will break on node v14+ and coul
	d be using insecure binaries. Upgrade to fsevents 2.
	npm WARN deprecated source-map-resolve@0.5.3: See https://github.com/lydell/sour
	ce-map-resolve#deprecated
	npm WARN deprecated source-map-url@0.4.1: See https://github.com/lydell/source-m
	ap-url#deprecated
	npm WARN deprecated urix@0.1.0: Please see https://github.com/lydell/urix#deprec
	ated
	npm WARN deprecated resolve-url@0.2.1: https://github.com/lydell/resolve-url#dep
	recated
	F:\Program Files\nodejs\babel-node -> F:\Program Files\nodejs\node_modules\babel
	-cli\bin\babel-node.js
	F:\Program Files\nodejs\babel-doctor -> F:\Program Files\nodejs\node_modules\bab
	el-cli\bin\babel-doctor.js
	F:\Program Files\nodejs\babel -> F:\Program Files\nodejs\node_modules\babel-cli\
	bin\babel.js
	F:\Program Files\nodejs\babel-external-helpers -> F:\Program Files\nodejs\node_m
	odules\babel-cli\bin\babel-external-helpers.js

	> core-js@2.6.12 postinstall F:\Program Files\nodejs\node_modules\babel-cli\node
	_modules\core-js
	> node -e "try{require('./postinstall')}catch(e){}"

	Thank you for using core-js ( https://github.com/zloirock/core-js ) for polyfill
	ing JavaScript standard library!

	The project needs your help! Please consider supporting of core-js on Open Colle
	ctive or Patreon:
	> https://opencollective.com/core-js
	> https://www.patreon.com/zloirock

	Also, the author of core-js ( https://github.com/zloirock ) is looking for a goo
	d job -)

	npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@^1.0.0 (node_modules\ba
	bel-cli\node_modules\chokidar\node_modules\fsevents):
	npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@
	1.2.13: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"
	})

	+ babel-cli@6.26.0
	added 234 packages from 119 contributors in 61.661s

	E:\HMV\Babel>

	Microsoft Windows [版本 6.1.7601]
	版权所有 (c) 2009 Microsoft Corporation。保留所有权利。

	E:\HMV\Babel>babel hzh.js
	"use strict";

	var input = [1, 2, 3];
	input.map(function (item) {
	return item + 1;
	});


	E:\HMV\Babel>

	# 转码结果写入一个文件
	# --out-file 或 -o 参数指定输出文件
	$ babel hzh.js --out-file huangzihan.js
	# 或者
	$ babel hzh.js --o huangzihan.js

	// hzh.js

	var input = [1, 2, 3];
	input.map(item => item + 1);

	// huangzihan.js

	"use strict";

	var input = [1, 2, 3];
	input.map(function (item) {
	return item + 1;
	});

	Microsoft Windows [版本 6.1.7601]
	版权所有 (c) 2009 Microsoft Corporation。保留所有权利。

	E:\HMV\Babel>babel hzh.js -o huangzihan.js

	E:\HMV\Babel>

	# 整个目录转码
	# --out-dir 或 -d 参数指定输出目录
	$ babel hzh1 --out-dir hzh2
	# 或者
	$ babel hzh1 -d hzh2

	// hzh11.js

	var hzh11 = [1, 2, 3];
	hzh11.map(item => item + 1);

	// hzh12.js

	var hzh12 = [1, 2, 3];
	hzh12.map(item => item + 1);

	Microsoft Windows [版本 6.1.7601]
	版权所有 (c) 2009 Microsoft Corporation。保留所有权利。

	E:\HMV\Babel>babel hzh1 -d hzh2
	hzh1\hzh11.js -> hzh2\hzh11.js
	hzh1\hzh12.js -> hzh2\hzh12.js

	E:\HMV\Babel>

	// hzh1.js

	var hzh11 = [1, 2, 3];
	hzh11.map(item => item + 1);

	// hzh2.js

	var hzh12 = [1, 2, 3];
	hzh12.map(item => item + 1);

	Microsoft Windows [版本 6.1.7601]
	版权所有 (c) 2009 Microsoft Corporation。保留所有权利。

	E:\HMV\Babel>babel hzh1 -d hzh2 -s
	hzh1\hzh11.js -> hzh2\hzh11.js
	hzh1\hzh12.js -> hzh2\hzh12.js

	E:\HMV\Babel>

	{
	// ...

	"devDependencies": {
	"babel-cli": "^6.0.0"
	},
	"scripts": {
	"build": "babel src -d lib"
	},
	}

	Microsoft Windows [版本 6.1.7601]
	版权所有 (c) 2009 Microsoft Corporation。保留所有权利。

	E:\HMV\Babel>babel-node
	> (hzh => hzh * 3)(2)
	6
	>

	Microsoft Windows [版本 6.1.7601]
	版权所有 (c) 2009 Microsoft Corporation。保留所有权利。

	E:\HMV\Babel>babel-node hzh.js
	12