JavaScript设计模式之单例模式

class Singleton1{
    /*核-一个接收实例的静态成员*/
    private static people:Singleton1;
    private name:string;


    /*核心-私有构造函数*/
    private constructor(name:string) {
        this.name = name;
    }


    /*核心-获取实例*/
    public static getInstance():Singleton1{
        if(Singleton1.people == null){
            Singleton1.people = new Singleton1("懒汉式单例模式");
        }
        return Singleton1.people;
    }


    public say():void{
        console.log(`${this.name}`);
    }
}


/*测试代码*/
let people = Singleton1.getInstance();
people.say(); //懒汉式单例模式

class Singleton2{
    private static people:Singleton2 = new Singleton2('饿汉式单例模式');
    private name:string;


    private constructor(name) {
        this.name = name;
    }


    public static getInstance():Singleton2{
        return Singleton2.people;
    }


    public say():void{
        console.log(this.name);
    }
}


/*测试代码*/
let s = Singleton2.getInstance();
s.say(); //饿汉式单例模式

function singletonIfy(className):ProxyConstructor{
    return new Proxy(className.prototype.constructor,{
        construct(target: ProxyConstructor, argArray: any, newTarget?: any): object {
            if(!this.instance){
                // @ts-ignore
                this.instance = new target(...argArray);
            }
            return this.instance;
        }
    })
}


class MyClass{
    private readonly msg: string;
    constructor(msg) {
        this.msg = msg;
    }
    printMsg():void{
        console.log(this.msg);
    }
}


let MySingletonClass;
MySingletonClass = singletonIfy(MyClass);
const obj1 = new MySingletonClass('first');
obj1.printMsg(); //first
const obj2 = new MySingletonClass('second');
obj2.printMsg(); //first