typescript(以下简称为ts)是js的超集,它有独立的编译器,为js提供了很多种类型,能够避免js的鸭子类型所产生的类型错误,这种错误有时候是致命的,以至于难以发现。因此我们希望在node中也引入typescript,使程序的编写效率有大大的提高。
首先我们需要安装typescript的tsc编译器,tsc能够把ts转换为js,因为node的解释器是不认ts的,因此在运行node应用之前需要把ts转换为js。
cnpm install --save typescript
等待安装完毕后可以查看一下tsc的版本
➜ dist tsc -v
Version 2.6.1
安装完tsc ,我们就可以开始一个小demo了,新建一个node_project,把它作为node 的项目目录
mkdir node_project
cd node_project
npm init
...
tsc --init
npm init是把该目录初始化为一个npm项目,之后执行的tsc —init是为了让tsc帮助我们创建tsconfig文件,tsconfig是tsc每次编译时都会检查的一个配置文件。
tsconfig.json
{
"compilerOptions": {
/* Basic Options */
"target": "es5", /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', or 'ESNEXT'. */
"module": "commonjs", /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 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. */
// "sourceMap": true, /* Generates corresponding '.map' file. */
// "outFile": "./", /* Concatenate and emit output to single file. */
"outDir": "./dist", /* Redirect output structure to the directory. */
"rootDir": "./src", /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
// "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. */
// "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. */
// "preserveSymlinks": true, /* Do not resolve the real path of symlinks. */
/* 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. */
}
}
这里只需关注一下outDir和rootDir。outDir是tsc编译后输出的js文件的目录,这里我把它输出在dist目录,rootDir是源文件的目录,也就是需要被tsc编译的目录。
我们可以在src目录下编写一个简单的node程序
cd src
touch main.ts
main.ts
import * as http from 'http';
import { IncomingMessage, ServerResponse } from 'http';
let httpServer:http.Server = http.createServer((req:IncomingMessage,res:ServerResponse) => {
res.writeHead(200);
res.end('Hello Typescript!');
});
httpServer.listen(9999,() => console.log('listening'));
然后我们可以让tsc开启监视模式,根据源文件目录下的文件改变来编译ts文件
tsc -w
现在开始执行main.ts
cd dist
node main.js
可以看到运行成功!
这样虽然还是会有点麻烦,每次都要用node main.js来运行node程序,其实我们完全可以引入webpack来进行模块热更新,如果你需要的话。