create-react-app添加对TypeScript支持

背景

最近一直在重构react项目，由于项目历史原因，将之前parcel打包工具换成了webpack，并选择了使用create-react-app作为项目开发脚手架。
接着就是把项目中flow类型检查工具移除掉了，替换成typescript。

相关文档

• https://www.html.cn/create-react-app/docs/adding-typescript/
• https://www.typescriptlang.org/

让项目支持ts的两种方式

1. 使用typescript创建react-app项目

yarn create react-app my-app --typescript

2. 要将 TypeScript 添加到 Create React App 项目

yarn add typescript @types/node @types/react @types/react-dom @types/jest

在Create React App项目中添加支持ts

1. 安装typescript及声明类型

yarn add typescript @types/react @types/react-dom @types/node @types/jest

2. 配置tsconfig.json

{
  "compilerOptions": {
    "target": "es5",// 目标语言的版本
    "lib": ["dom", "dom.iterable", "es2015.promise", "esnext"],
    // 编译时引入的 ES 功能库，包括：es5 、es6、es7、dom 等。// 如果未设置，则默认为： target 为 es5 时: ["dom", "es5", "scripthost"] 
    //target 为 es6 时: ["dom", "es6", "dom.iterable", "scripthost"]
    "allowJs": true, // 允许编译器编译JS，JSX文件
    "checkJs": true, // 允许在JS文件中报错，通常与allowJS一起使用
    "skipLibCheck": true,
    "esModuleInterop": true,// 允许export=导出，由import from 导入
    "allowSyntheticDefaultImports": true,
    "strict": true,// 开启所有严格的类型检查
    "forceConsistentCasingInFileNames": true,
    "module": "esnext",// 生成代码的模板标准
    "moduleResolution": "node",// 模块解析策略，ts默认用node的解析策略，即相对的方式导入
    "resolveJsonModule": true,
    "isolatedModules": true,
    "noEmit": true,// 不输出文件,即编译后不会生成任何js文件
    "jsx": "react",//在 .tsx 中支持 JSX ：React 或 Preserve
    "strictFunctionTypes": false,// 不允许函数参数双向协变
    "downlevelIteration": true,// 降级遍历器实现，如果目标源是es3/5，那么遍历器会有降级的实现
    "noFallthroughCasesInSwitch": true,// 防止switch语句贯穿(即如果没有break语句后面不会执行)
    "baseUrl": "./src" // 解析非相对模块的基地址，默认是当前目录
  },
  "include": ["src", "**/*.ts", "**/*.tsx"],
  "exclude": ["./node_modules"]
}

这里需要注意的是，现有项目由于都是js文件，所有我们需要开启allowJs为true支持编译js文件，让之前的项目可以正常跑起来，
然后再慢慢的将之前的js代码改造成ts代码。

这里再说一下关于jsx、tsx和ts的区别

• JSX，是一个 JavaScript 的语法扩展，在React框架中开始流行-
• tsx，如要在typescript中使用jsx语法，则扩展名命名文件使用.tsx后缀
• ts，typescript默认使用.ts扩展名

3. 创建Content.tsx文件和content.ts文件

//Content.tsx

import React from 'react'
import { user } from './content'

const Content: React.FC = () => {
  const { name } = user
  return (
    <div>
      hi,{name}
    </div>
  )
}

export default Content


//content.ts

interface User {
  name: string
}

export const user: User = {
  name: 'Kerry'
}

其他

上面的tsconfig.json文件我们也可以通过命令的方式进行创建

tsc --init

这里如果报错command not found: tsc，需要使用全局方式安装typescript yarn global add typescript

执行以上命令后，会为我们再根目录下生成一个默认的tsconfig.json文件

• compilerOptions 用来配置编译选项
• include 指定编译目录
• exclude 排除的编译的目录

更多配置可以查看https://www.typescriptlang.org/docs/handbook/tsconfig-json.html

{
  "compilerOptions": {
    /* Visit https://aka.ms/tsconfig.json to read more about this file */

    /* Basic Options */
    // "incremental": true,                   /* Enable incremental compilation */
    "target": "es5",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', or 'ESNEXT'. */
    "module": "commonjs",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 'es2020', or 'ESNext'. */
    // "lib": [],                             /* Specify library files to be included in the compilation. */
    // "allowJs": true,                       /* Allow javascript files to be compiled. */
    // "checkJs": true,                       /* Report errors in .js files. */
    // "jsx": "preserve",                     /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
    // "declaration": true,                   /* Generates corresponding '.d.ts' file. */
    // "declarationMap": true,                /* Generates a sourcemap for each corresponding '.d.ts' file. */
    // "sourceMap": true,                     /* Generates corresponding '.map' file. */
    // "outFile": "./",                       /* Concatenate and emit output to single file. */
    // "outDir": "./",                        /* Redirect output structure to the directory. */
    // "rootDir": "./",                       /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
    // "composite": true,                     /* Enable project compilation */
    // "tsBuildInfoFile": "./",               /* Specify file to store incremental compilation information */
    // "removeComments": true,                /* Do not emit comments to output. */
    // "noEmit": true,                        /* Do not emit outputs. */
    // "importHelpers": true,                 /* Import emit helpers from 'tslib'. */
    // "downlevelIteration": true,            /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
    // "isolatedModules": true,               /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */

    /* Strict Type-Checking Options */
    "strict": true,                           /* Enable all strict type-checking options. */
    // "noImplicitAny": true,                 /* Raise error on expressions and declarations with an implied 'any' type. */
    // "strictNullChecks": true,              /* Enable strict null checks. */
    // "strictFunctionTypes": true,           /* Enable strict checking of function types. */
    // "strictBindCallApply": true,           /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
    // "strictPropertyInitialization": true,  /* Enable strict checking of property initialization in classes. */
    // "noImplicitThis": true,                /* Raise error on 'this' expressions with an implied 'any' type. */
    // "alwaysStrict": true,                  /* Parse in strict mode and emit "use strict" for each source file. */

    /* Additional Checks */
    // "noUnusedLocals": true,                /* Report errors on unused locals. */
    // "noUnusedParameters": true,            /* Report errors on unused parameters. */
    // "noImplicitReturns": true,             /* Report error when not all code paths in function return a value. */
    // "noFallthroughCasesInSwitch": true,    /* Report errors for fallthrough cases in switch statement. */

    /* Module Resolution Options */
    // "moduleResolution": "node",            /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
    // "baseUrl": "./",                       /* Base directory to resolve non-absolute module names. */
    // "paths": {},                           /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
    // "rootDirs": [],                        /* List of root folders whose combined content represents the structure of the project at runtime. */
    // "typeRoots": [],                       /* List of folders to include type definitions from. */
    // "types": [],                           /* Type declaration files to be included in compilation. */
    // "allowSyntheticDefaultImports": true,  /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
    "esModuleInterop": true,                  /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
    // "preserveSymlinks": true,              /* Do not resolve the real path of symlinks. */
    // "allowUmdGlobalAccess": true,          /* Allow accessing UMD globals from modules. */

    /* Source Map Options */
    // "sourceRoot": "",                      /* Specify the location where debugger should locate TypeScript files instead of source locations. */
    // "mapRoot": "",                         /* Specify the location where debugger should locate map files instead of generated locations. */
    // "inlineSourceMap": true,               /* Emit a single file with source maps instead of having a separate file. */
    // "inlineSources": true,                 /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */

    /* Experimental Options */
    // "experimentalDecorators": true,        /* Enables experimental support for ES7 decorators. */
    // "emitDecoratorMetadata": true,         /* Enables experimental support for emitting type metadata for decorators. */

    /* Advanced Options */
    "skipLibCheck": true,                     /* Skip type checking of declaration files. */
    "forceConsistentCasingInFileNames": true  /* Disallow inconsistently-cased references to the same file. */
  }
}

参考阅读

• https://zhuanlan.zhihu.com/p/100744558
• https://blog.csdn.net/qq_36154659/article/details/107645982
• https://stackoverflow.com/questions/64115884/error-when-updating-create-react-app-to-4-0-with-typescript-template