安装，创建项目

• 安装nodejs
• 安装typescript: npm install -g typescript
• 初始化项目：

npm init
npx tsc --init

• 启动

npm i -D nodemon

npx nodemon -w dist dist/index.js

Modules

• export ...

import { ... } from ...

• export default ...

import ... from ...

• export default 同一个module只能存在一个， export可以多个；
• 可以用export ... as ...修改需要的调用名.

Types

• Boolean let b: boolean = true;
• Number let num: number = 1 + 0b1 + 0o1 + 0x1;
• String

const hello: string = "hello";
const world: string = 'hello';
const helloWorld = `
  ${hello}
  ${world}
`;

• Null & undefined

let n: null = null;
let u: undefined = undefined;
let someNumber: number = null;
`strictNullChecks: true`

• Object type primitveTypes = boolean | number | string | symbol | null | undefined;
• Void
• Array

let array1: string[] = ['x', 'y'];
let array1: Array<string> = array1;

• Tuple let tuple: [string, number] = ['a', 1];
• Enum

enum Color {
  Red,
  Green,
  Blue
}
let myColor: Color = Color.blue;
cosole.log(Color.Red, Color.Green); //1, 2
enum Color {
  Red = 2,
  Green = 1,
  Blue = 4
}
console.log(Color[4]); //Blue

enum Color {
  Red = 'red',
  Green = 'green',
  Blue = 'blue'
}
console.log(Color['red']); //undfined

• Any

let ANY: any;
ANY = 'string';
ANY = 1;

• Type assertions

const email = document.getElementById('email');
if(email) {
  email.addEventListener('change', e => {
    const input = e.currentTarget as HTMLInputElement; //<HTMLInputElement>e.currentTarget
    console.log(input.value);
  )
}

Interface

interface A {
  someProp: number;
}
interface B {
  someProp: number;
  anotherProp: number;
}
let a = {someProp: 1}

• index Signature

interface A {
  someProp: number;
  [key: string]: number;
}
const a: A = {someProp: 'string'}

• Call signature

interface Sum {
  (a: number, b: number): number;
  prop1: string;
}
const sum: Sum = (a, b) => a + b;
sum.prop1 = "prop1";

• Extending Interface

interface Parent { x: string; }
interface Parent1 { y: string; }
interface Parent2 { z: string; }
interface Child extends Parent, Parent1, Parent2 {}
let child: Child = {x: 'a', y: 'b', z: 'c'}