之前都是用js开发的nodejs应用，今天试着用typpescript写服务端程序，这里遇到的一些坑总结一下：
1: 首先创建一个文件夹用于存放nodejs项目，这里起名为 node-ts-server
2：执行npm init项目会生成一个package.json文件
3：安装typescript npm install typescript
4: 执行tsc --init 自动生成tsconfig.json文件,修改为以下配置，可以根据项目需求灵活改动
{
"compilerOptions": {
/* 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": "./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. */
// "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'). */
"watch": true,
/* 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 */
"forceConsistentCasingInFileNames": true /* Disallow inconsistently-cased references to the same file. */
},
"include": ["src/**/*.ts"],
"exclude": ["node_modules/*.ts"]
}
5：创建源代码文件夹src,添加一个测试用的ts文件 app.ts也就是package.json文件里面的入口文件，创建之前先安装一下express
npm install express --save不熟悉express的可以移步到express的官方文档：express 文档
但是安装完之后在写app.ts文件引入 express 会爆红 import express from "express"这是因为没有声明express这就需要安装 @types/express 执行 npm install --save @types/express 就不会爆红了
app.ts如下：
import express from "express";
const app = express();
const port = 3000;
app.listen(port,() => {
console.log("a server is listen on port:",port);
})写好了这个ts文件我们想直接运行ts文件怎么办呢，这时候ts-node就派上用场了，全局安装一下：
npm install -g ts-node现在执行tsc 命令就会生成一个dist文件夹到你的项目里面了，也可以直接执行
ts-node ./src/app.ts就启动服务了
现在还有一个需求就是每当我改动src目录项的ts文件的时候，系统服务会重新启动，这时候就要用到nodemon这个东西了，不了解的可以度娘一下，
开始安装 nodemon
npm install -g nodemon6: 在package.json文件中添加一个script: "start": "nodemon --watch src/**/*.ts --exec \"ts-node\" src/app.ts"
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1",
"start": "nodemon --watch src/**/*.ts --exec \"ts-node\" src/app.ts"
},大功告成，这样每次改动都会在下面的控制台有如下输出：
> [email protected] start /Users/lck/js_study/node-ts-server
> nodemon --watch src/**/*.ts --exec "ts-node" src/app.ts
[nodemon] 2.0.3
[nodemon] to restart at any time, enter `rs`
[nodemon] watching path(s): src/**/*.ts
[nodemon] watching extensions: ts,json
[nodemon] starting `ts-node src/app.ts`
a server is listen on port: 3000
[nodemon] restarting due to changes...
[nodemon] starting `ts-node src/app.ts`
a server is listen on port: 3000