使用typescript构建Koa应用

1.首先需要构建package.json文件：

执行命令：npm init进行初始化
修改package.json如下：

{
  "name": "js_server",
  "version": "1.0.0",
  "description": "a server use js to run",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@types/koa": "^2.0.46",
    "@types/koa-router": "^7.0.31",
    "nodemon": "^1.18.4",
    "ts-node": "^7.0.1",
    "typescript": "^3.0.3"
  }
}

2.安装typescript以及其依赖库：

npm i koa koa-router
npm i --save-dev typescript ts-node nodemon  // nodemon主要用于热加载APP
npm i --save-dev @types/koa @types/koa-router

3.构建tsconfig.json

此时的项目结构：

项目结构.png

{
    "compilerOptions": {
        "module": "commonjs",
        "target": "es2017",
        "noImplicitAny": true,
        "moduleResolution": "node",
        "sourceMap": true,
        "outDir": "dist",  // TS文件编译后会放入到此文件夹内
        "baseUrl": ".",
        "paths": {
            "*": [
                "node_modules/*",  //根据项目的路径指定
                "src/types/*"      //根据项目的路径指定
            ]
        }
    },
    "include": [
        "src/**/*"                //根据项目的路径指定
    ]
}

4.构建hello world 的APP

import * as Koa from 'koa'
import * as Router from 'koa-router'

const app = new Koa();
const router = new Router();

router.get('/*',async(ctx) => {
    ctx.body = "Hellow World !";
})

app.use(router.routes());

app.listen(3000);

console.log('Server is runing !!')

5.配置热加载

需要在packge.json配置中修改scripts如下：

"scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "tsc && node dist/app.js",
    "watch-server":"nodemon --watch ./src/app.ts -e ts,tsx --exec ts-node ./src/app.ts"   
 },

6.运行APP

npm run watch-server