eslint — js书写规范
一、安装
npm install -g eslint 安装eslint
编辑器安装插件eslint（具体安装方法根据不同编辑器而不同）
二、使用
使用方法一：
eslint --init npm中用命令新建eslintrc.js文件
eslint yourfile.js npm中用命令检查自己文件中的错误
使用方法二：
手动在项目的根目录下新建eslintrc.*文件（.js、.json、.yaml、.yml等），进行配置（具体配置规则详见下文），即可在安装好eslint的编辑器中查看到出现错误的位置。
三、配置：http://eslint.org/docs/rules/ (以下规则文件配置一个即可，置于项目根目录下)
(1).eslintrc文件中进行配置 http://eslint.org/docs/user-guide/configuring
{
"rules": {
"semi": ["error", "always"],
"quotes": ["error", "double"]
}
}
四、其他
1.在样式之前标注“/* eslint-disable */”，可忽略配置的规则；标注“/* esint-enable */“，开启配置的规则
2.“/* eslint-enable */“必须在“/* eslint-disable */”之后使用
3.忽略指定的内容：新建一个.eslineignore文件，例如：
# /node_modules/* and /bower_components/* ignored by default
# Ignore built files except build/index.js
build/*
!build/index.js
通过命令 eslint --ignore-path .eslintignore file.js可检测是否被忽视
4.enlint 有很多的rules，为了改变rule的设置，可以设置rule ID等同于一些规则属性：如
"off" or 0 关闭规则
"warn" or 1 打开规则，出现警告提示
"error" or 2 打开规则，出现错误提示
规则可如下定义：
"rules": {
"camel_case": 2
}
五、配置文件
{
"rules": {
"array-callback-return": "error",
"indent": ["error", 4, {"SwitchCase": 1}],
"block-spacing": "error",
"brace-style": ["error", "1tbs"],
"camelcase": ["error", { "properties": "never" }],
"callback-return": ["error", ["cb", "callback", "next"]],
"comma-spacing": "error",
"comma-style": ["error", "last"],
"consistent-return": "error",
"curly": ["error", "all"],
"default-case": "error",
"dot-notation": ["error", { "allowKeywords": false }],
"eol-last": "error",
"eqeqeq": "error",
"guard-for-in": "error",
"key-spacing": ["error", { "beforeColon": false, "afterColon": true }],
"keyword-spacing": "error",
"lines-around-comment": ["error", {
"beforeBlockComment": true,
"afterBlockComment": false,
"beforeLineComment": true,
"afterLineComment": false
}],
"new-cap": "error",
"newline-after-var": ["error", "never"],
"new-parens": "error",
"no-array-constructor": "error",
"no-invalid-this": "error",
"no-multi-spaces": "error",
"no-redeclare": "error",
"no-return-assign": "error",
"no-spaced-func": "error",
"no-trailing-spaces": "error",
"semi": "error",
"semi-spacing": "error",
"quotes":["error","double"],
"space-before-function-paren": ["error", "never"],
"space-in-parens": "error",
"space-infix-ops": "error",
"space-unary-ops": ["error", {"words": true, "nonwords": false}],
"spaced-comment": "error",
"yoda": ["error", "never"],
"no-mixed-requires": "error",
"handle-callback-err": ["error", "err"]
}
}
六、配置文件说明
| 属性名 | 属性值 | 描述 |
| [array-callback-return](http://eslint.org/docs/rules/array-callback-return) | "error" | Array执行回调函数返回语句 |
| [indent](http://eslint.org/docs/rules/indent) | ["error", 4, {"SwitchCase": 1}] | 缩写格式的一致性 |
| [block-spacing](http://eslint.org/docs/rules/block-spacing) | "error" | 禁止执行空间内出现'-' |
| [brace-style](http://eslint.org/docs/rules/brace-style) | ["error","1tbs"] | 代码书写格式验证 |
| [camelcase](http://eslint.org/docs/rules/camelcase) | ["error", { "properties": "never" }] | 属性命名规则可以不使用驼峰命名法 |
| [callback-return](http://eslint.org/docs/rules/callback-return) | ["error", ["cb", "callback", "next"]] | 回调函数需要return进行返回 |
| [comma-spacing](http://eslint.org/docs/rules/comma-spacing) | "error" | 不允许在逗号前面出现空格 |
| [comma-style](http://eslint.org/docs/rules/comma-style) | ["error", "last"] | 方数组元素、变量声明等直接需要逗号隔开 |
| [consistent-return](http://eslint.org/docs/rules/consistent-return) | "error" | 保持return返回的一致性 |
| [curly](http://eslint.org/docs/rules/curly) | ["error", "all"] | 函数或者条件判断时需要统一使用大括号 |
| [default-case](http://eslint.org/docs/rules/default-case) | "error" | switch语句中必须有default条件 |
| [dot-notation](http://eslint.org/docs/rules/dot-notation) | ["error", { "allowKeywords": false }] | 不允许关键字出现在变量中 |
| [eol-last](http://eslint.org/docs/rules/eol-last) | "error" | 代码间间隔出现一行 |
| [eqeqeq](http://eslint.org/docs/rules/eqeqeq) | "error" | 消除不安全类型的全等操作 |
| [guard-for-in](http://eslint.org/docs/rules/guard-for-in) | "error" | for循环中过滤掉一下不被需要的行为 |
| [key-spacing](http://eslint.org/docs/rules/key-spacing) | ["error", { "beforeColon": false, "afterColon": true }] | 键和值前保留一个空格 |
| [keyword-spacing](http://eslint.org/docs/rules/keyword-spacing) | "error" | 确保字符前后空格的一致性 |
| [lines-around-comment](http://eslint.org/docs/rules/lines-around-comment) | ["error", { "beforeBlockComment": true, "afterBlockComment": false, "beforeLineComment": true, "afterLineComment": false }] | 注释前需要空行，注释后不需要空行 |
| [new-cap](http://eslint.org/docs/rules/new-cap) | "error" | 构造函数首字母需要大写 |
| [newline-after-var](http://eslint.org/docs/rules/newline-after-var) | ["error", "never"] | var定义后不空行 |
| [new-parens](http://eslint.org/docs/rules/new-parens) | "error" | 没有参数时，构造函数也需要添加括号 |
| [no-invalid-this](http://eslint.org/docs/rules/no-invalid-this) | "error" | 不允许关键字this在函数或者类的外面 |
| [no-multi-spaces](http://eslint.org/docs/rules/no-multi-spaces) | "error" | 不允许键和值之间存在多个空格 |
| [no-redeclare](http://eslint.org/docs/rules/no-redeclare) | "error" | 不允许重复声明 |
| [no-return-assign](http://eslint.org/docs/rules/no-return-assign) | "error" | 不允许在return语句中任务 |
| [no-spaced-func](http://eslint.org/docs/rules/no-spaced-func) | "error" | 调用函数时，函数名和括号之间不能有空格。 |
| [no-trailing-spaces](http://eslint.org/docs/rules/no-trailing-spaces) | "error" | 不允许在语句后存在多余的空格 |
| [semi](http://eslint.org/docs/rules/semi) | "error" | 语句以分号结尾 |
| [semi-spacing](http://eslint.org/docs/rules/semi-spacing) | "error" | 分号前后不能有空格 |
| [quotes](http://eslint.org/docs/rules/quotes) | ["error","double"] | 使用双引号 |
| [space-before-function-paren](http://eslint.org/docs/rules/space-before-function-paren） | "space-before-function-paren": ["error", "never"] | 不允许函数括号之间存在空格 |
| [space-in-parens](http://eslint.org/docs/rules/space-in-parens) | "error" | 不允许在括号里面存在空格 |
| [space-infix-ops](http://eslint.org/docs/rules/space-infix-ops) | "error" | 插入符合变量之间需要添加一个空格 |
| [space-unary-ops](http://eslint.org/docs/rules/space-unary-ops) | ["error", {"words": true, "nonwords": false}] | 允许一元运算符操作 |
| [spaced-comment](http://eslint.org/docs/rules/spaced-comment) | "error" | 注释前需要一个空格 |
| [yoda](http://eslint.org/docs/rules/yoda) | ["error", "never"] | 条件语句中，变量在赋值语句的前面 |
| [no-mixed-requires](http://eslint.org/docs/rules/no-mixed-requires) | "error" | 不允许混合requires文件 |
| [no-new-require](http://eslint.org/docs/rules/no-new-require) | "error" | 不允许new require出现 |
| [no-path-concat](http://eslint.org/docs/rules/no-path-concat) | "error" | 不允许路径以_链接 |
| [handle-callback-err](http://eslint.org/docs/rules/handle-callback-err) | ["error", "err"] | 处理错误的回调函数 |
