TypeScript类型声明文件

Declaration files give you the ability to give TypeScript more information about how a function or class is structured.
Declaration files do not have any implementation code; they simply describe the types and structure for the elements used in the module.
Declaration files are used solely for the benefit of the developer and are only utilized by the IDE.

三斜线指令

/// <reference types=“UMDModuleName/globalName” />

• TypeScript的早期模块化标签,用来引用其他模块的类型定义文件
• 三斜线指令必须放在文件的最顶端，三斜线指令的前面只允许出现单行或多行注释
• 现在使用import替代三斜线指令

全局变量

• declare let/const: 声明全局变量
• declare function: 声明全局方法
• declare class: 声明全局类
• declare enum: 声明全局枚举类型
• declare namespace: 声明全局对象（含有子属性）
• interface/type: 声明全局类型

Example

// 变量
declare let userName: string;

declare const wx: any;

// 函数、函数重载
declare function getName(uid: number): string;
declare function getName(): string;
declare function getName(cb: () => any): any;

// 类
declare class Course {
  cid: number;
  constructor(cid){};
  getCoursePrice(): number;
}

// 枚举
declare enum Status {
  Loading,
  Success,
  Failed,
}

// 接口 interface declare 可以不需要
interface CourseInfo {
  cid: number;
  name: string;
}

interface CGIData<T> {
  data: T;
  retcode: 0;
}

// 命名空间
declare namespace User {
  // 局部 Test.User
  interface User {
    name: string;
    age: number;
  }

  function getUserInfo(name: string): User {
    return "";
  }
  namespace fn {
    function extend(obj: any): any;
  }
}


// 声明合并
declare function User(id: number): string;

编译时自动生成.d.ts文件

{
    "compilerOptions": {
        "declaration": true,
    }
}