TypeScript 初体验

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Typescript 介绍

  • typescript 是由微软开发的一款开源的编程语言。
  • typescript 是 Javascript 的超集，遵循最新的 ES6、Es5 规范。TypeScript 扩展了 JavaScript 的语法。
  • typescript 更像后端 java、C#这样的面向对象语言，可以让 js 开发大型企业项目。
  • 谷歌也在大力支持 Typescript 的推广，谷歌的 angular2.x+就是基于 Typescript 语法。
  • 最新的 Vue 、React 也可以集成 TypeScript。
  • Nodejs 框架 Nestjs、midway 中用的就是 TypeScript 语法。

为什么要使用 TypeScript

  • 类型推演与类型匹配
  • 开发编译时报错
  • 极大程度的避免了低级错误
  • 支持 JavaScript 最新特性（包含 ES6\7\8）

Typescript 安装 编译

在使用 npm 命令之前电脑必须得安装 nodejs

安装

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npm install -g typescript
或者
cnpm install -g typescript
或者
yarn global add typescript

运行

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tsc helloworld.ts

注意：如果电脑上面没有安装过 cnpm，请先安装 cnpm

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npm install -g cnpm --registry=https://registry.npm.taobao.org

注意：如果电脑上面没有安装过 yarn 请先安装 yarn:

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npm install -g yarn
或者
cnpm install -g yarn

Typescript 开发工具 Vscode 自动编译.ts 文件

创建 tsconfig.json 文件

tsc --init 生成配置文件

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tsc --init

修改编译后的 js 输出目录 outDir: "./js"

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// tsconfig.json
{
  "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": "./js" /* 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. */
    // "noUncheckedIndexedAccess": true,      /* Include 'undefined' in index signature results */

    /* 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. */
  }
}

tsc:监视-tsconfig.json

  • 老版本 vscode 点击: 任务->运行任务-> tsc:监视-tsconfig.json 然后就可以自动生 成代码了
  • 最新版本 vscode 点击: 终端->运行任务->typescript->tsc:监视-tsconfig.json 然后就 可以自动生成代码了

注意

VSCode 自动编译 TypeScript 时一直报 typeconfig 配置文件路径找不到的错误。纠结很久，终于找到解决办法： 错误如下： error TS5058: The specified path does not exist：d:\typescripttsconfig.json 错误的

错误的原因是修改了 vscode 默认的系统终端类型。我改为了 git bash 了，所以一直不成功。

解决办法就是改回默认的终端类型就能解决这个问题了。