TypeScript 基础

基础

1. 类型推断

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let a = 'abc'
a = 'def' // a = 1 会报错

2. 类型注解

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let a: string

3. 类型断言

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let numArr = [1, 2, 3]
const result = numArr.find(item => item > 2) as number // 操作的最终结果，断言是 number 类型
result * 5

4. 基础类型和联合类型

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//基础类型
let v1: string = 'abc'
let v2: number = 10
let v3: boolean = true
let nu: null = null
let un: undefined = undefined

//联合类型
let v4: string | null = null
let v5: 1 | 2 | 3 = 2

5. 数组、元组、枚举

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//数组
let arr: number[] = [1, 2, 3]
let arr1: Array<string> = ['a', 'b', 'c']

//元组
let t1: [number, string, number] = [1, 'a', 2]
let t1: [number, string, number?] = [1, 'a'] // ?表示可有可无

//枚举
enum MyEnum {A, B, C} // 默认从0开始分配
console.log(MyEnum.A)  console.log(MyEmum[0])//这俩访问的是同一个

// void 默认是 undefined

6. 函数

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function MyFn(a: number, b: string, c?: boolean, ...rest: number[]): number {// 可选参数要在最后
  return 100;
}
const f = MyFn(20, 'abc', true, 1, 2, 3, 4, 5);

7. 接口

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interface Obj {
  name: string;
  age: number;
}

const obj: Obj = {
  name: 'a',
  age: 10,
};

8. 类型别名

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type MyUserName = string | number;
let a: MyUserName = 10;
let b: MyUserName = 'Luke';

9. 泛型

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function myFn<T>(a: T, b: T): T[] {
  return [a, b];
}

myFn<number>(1, 2);
myFn<string>('a', 'b');

进阶

1. 函数重载

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function hello(name: string): string;

function hello(age: number): string;

function hello(value: string | number): string {
  if (typeof value === "string") {
    return "你好，我的名字是" + value;
  } else if (typeof value === "number") {
    return "你好，我的年龄是${value}";
  } else {
    return "非法格式";
  }
}

hello("abc");
hello(18);

2. 接口继承

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interface Parent {
  prop1: string;
  prop2: number;
}

interface Child extends Parent {
  prop3: boolean;
}

const myObj: Child = {
  prop1: 'a',
  prop2: 1,
  prop3: true,
};

3. 类的修饰符

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class Article {
  public title: string; // 不写就是 public
  content: string;
  aaa?: string;
  bbb = 100;

  private ccc?: string;
  protected ddd?: string;

  static author: string; // static 要写在最后
  private static readonly: string = "Luke"; // 只读且 private

  constructor(title: string, content: string) {
    this.title = title;
    this.content = content;
  }
}

const a = new Article("标题", "内容");

// a.ccc 报错
a.title;
// a.ddd 报错
Article.author;

class B extends Article {
  constructor(title: string, content: string) {
    super(title, content);
    this.ddd;
  }
}

4. 存取器

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class User {
  private _password: string = "";

  get password(): string {
    return "******";
  }

  set password(newPass: string) {
    this._password = newPass;
  }
}

const u = new User();
console.log(u.password);

5. 抽象类

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没啥用

6. 类实现接口

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没啥用

7. 泛型类

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没啥用