老吕教程--01后端Node.js框架搭建（安装调试KOA2）

今天开始从零搭建后端框架，后端框架基于Koa2，通过Typescript语言编写。

在写后端框架之前，自己也了解过Express，感觉Koa2更加灵活，由于有多年后端研发经验，所以采用Koa2，简单敏捷灵活。

1. 安装Koa2

首先要安装Node.js，这个就不赘述，安装最新版即可。开发IDE使用VisualStudio Code，绝对推荐。

使用vs code打开自己新建的server文件夹，使用控制台命令行，敲入以下命令：

1.1 初始化package.json文件：（根据提示回车）

npm init

1.2 安装Koa2：

npm install koa

1.3 添加index.js文件，尝试第一次运行Koa2，敲入以下代码

const Koa = require('koa');
const app = new Koa();

app.use(async ctx => {
  ctx.body = 'Hello World';
});

app.listen(3000);

1.4 然后F5运行，打开浏览器，输入localhost:3000，如下图

2. 安装Typescript

由于我个人比较喜欢TS，所以想尝试使用，对后期开发都有好处（前端也用TS，TS流行啊）。

2.1 全局安装TS

npm i typescript -g

2.1 添加TS配置文件：tsconfig.json

tsc --init

执行后，会出现tsconfig.json文件

2.2 打开tsconfig.json，进行配置

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

    /* Basic Options */
    // "incremental": true,                   /* Enable incremental compilation */
    "target": "es2017",
    /* 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": "./bin",
    /* 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. */
    // "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. */
  },
  "include": [
    "src/**/*.ts",
    "src/*.ts",
    "src/*"
  ],
  "exclude": [
    "node_modules"
  ],
  "watch": true
}

2.3 安装@types/node

npm i @types/node

2.4 修改index.js为index.ts，修改内部代码

const Koa = require('koa');
const app = new Koa();

app.use(async (ctx: any) => {
  ctx.body = 'Hello World';
});

console.log('app server start on port 3000...')
app.listen(3000);

2.5  通过F5直接在vs code中进行调试，Ctrl + Shift + B（windows），创建task.json

{
    // See https://go.microsoft.com/fwlink/?LinkId=733558
    // for the documentation about the tasks.json format
    "version": "2.0.0",
    "tasks": [
        {
            "label": "typescript",
            "type": "typescript",
            "tsconfig": "tsconfig.json",
            "problemMatcher": [
                "$tsc"
            ]
        }
    ]
}

2.6 在vs code 右侧，debug模式，添加配置

2.7 自动生成launch.json文件，修改为：

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "type": "node",
            "request": "launch",
            "name": "Launch Program",
            "preLaunchTask": "typescript",
            "protocol":"inspector",
            "program": "${workspaceFolder}/index.ts",
            "outFiles": [
                "${workspaceFolder}/bin/*.js"
            ]
        }
    ]
}

2.8 按F5运行，控制台输出和页面显示如下：