TypeStript 入门 - 12：扩展变量类型

拓展全局类型String

//! declare 包裹声明
declare global {
 //! 1. 拓展全局类型String的方法声明
 interface String {
  double(): string;
 }
}

//! 1. 实现拓展全局类型String的方法
String.prototype.double = function () {
 return this + "," + this;
}

let str = 'pt';
console.log(str.double());

合并声明

拓展类：同名interface合并

//! 1.同名interface合并：利用interface 把多个同名interface声明合并
interface Animal {
 name: string
}
interface Animal {
 age: number
}

let a: Animal = { name: 'pt', age: 18 };

扩展类: class 与namespace 合并

//! 2.扩展类: class 与namespace 合并
class Form { }
namespace Form {
 export const type = 'form'
}

let f1: Form = { type: "xx" };
console.log(Form.type); //form
console.log(f1);    //{type:'xx'}

拓展方法: function 与 namespace 合并

//! 3.拓展方法: function 与 namespace 合并
function getName() { }
namespace getName {
 export const type = 'form'
}
console.log(getName.type);//form

拓展枚举：enum 与 namespace 合并

//! 4.拓展枚举：enum 与 namespace 合并
enum Seasons {
 Spring = 'Spring',
 Summer = 'Summer'
}
namespace Seasons {
 export let Autumn = 'Autumn';
 export let Winter = 'Winter'
}
console.log(Seasons.Spring);//Spring
console.log(Seasons.Autumn);//Autumn

交叉拓展类：利用&交叉拓展

type Animal = {
 age: Number
}

type Person = {
 name: String
}

type PersonInfo = Animal & Person & {
 address: string
}

let personInfo: PersonInfo;
personInfo = { age: 11, name: "pt", address: "123" };

总结

• 配置tsconfig.json  "declaration": true 可生成声明文件配置