背景

最近一直在重構react專案，由於專案歷史原因，將之前parcel打包工具換成了webpack，並選擇了使用create-react-app作為專案開發腳手架。
接著就是把專案中flow型別檢查工具移除掉了，替換成typescript。

相關文件

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

讓專案支援ts的兩種方式

1. 使用typescript建立react-app專案

yarn create react-app my-app --typescript

2. 要將 TypeScript 新增到 Create React App 專案

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

在Create React App專案中新增支援ts

1. 安裝typescript及宣告型別

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

2. 配置tsconfig.json

{
  "compilerOptions": {
    "target": "es5",// 目標語言的版本
    "lib": ["dom", "dom.iterable", "es2015.promise", "esnext"],
    // 編譯時引入的 ES 功能庫，包括：es5 、es6、es7、dom 等。// 如果未設定，則預設為： target 為 es5 時: ["dom", "es5", "scripthost"] 
    //target 為 es6 時: ["dom", "es6", "dom.iterable", "scripthost"]
    "allowJs": true, // 允許編譯器編譯JS，JSX檔案
    "checkJs": true, // 允許在JS檔案中報錯，通常與allowJS一起使用
    "skipLibCheck": true,
    "esModuleInterop": true,// 允許export=匯出，由import from 匯入
    "allowSyntheticDefaultImports": true,
    "strict": true,// 開啟所有嚴格的型別檢查
    "forceConsistentCasingInFileNames": true,
    "module": "esnext",// 生成程式碼的模板標準
    "moduleResolution": "node",// 模組解析策略，ts預設用node的解析策略，即相對的方式匯入
    "resolveJsonModule": true,
    "isolatedModules": true,
    "noEmit": true,// 不輸出檔案,即編譯後不會生成任何js檔案
    "jsx": "react",//在 .tsx 中支援 JSX ：React 或 Preserve
    "strictFunctionTypes": false,// 不允許函式引數雙向協變
    "downlevelIteration": true,// 降級遍歷器實現，如果目標源是es3/5，那麼遍歷器會有降級的實現
    "noFallthroughCasesInSwitch": true,// 防止switch語句貫穿(即如果沒有break語句後面不會執行)
    "baseUrl": "./src" // 解析非相對模組的基地址，預設是當前目錄
  },
  "include": ["src", "**/*.ts", "**/*.tsx"],
  "exclude": ["./node_modules"]
}
 

這裡需要注意的是，現有專案由於都是js檔案，所有我們需要開啟allowJs為true支援編譯js檔案，讓之前的專案可以正常跑起來，
然後再慢慢的將之前的js程式碼改造成ts程式碼。

這裡再說一下關於jsx、tsx和ts的區別

• JSX，是一個 JavaScript 的語法擴充套件，在React框架中開始流行-
• tsx，如要在typescript中使用jsx語法，則副檔名命名檔案使用.tsx字尾
• ts，typescript預設使用.ts副檔名

3. 建立Content.tsx檔案和content.ts檔案

//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檔案我們也可以通過命令的方式進行建立

tsc --init

這裡如果報錯command not found: tsc，需要使用全域性方式安裝typescript yarn global add typescript

執行以上命令後，會為我們再根目錄下生成一個預設的tsconfig.json檔案

• compilerOptions 用來配置編譯選項
• include 指定編譯目錄
• exclude 排除的編譯的目錄

更多配置可以檢視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. */
  }
}

參考閱讀

• 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