SOURCE

class SinglePerson {
    
    constructor(name,age) {
        this.name = name
        this.age = age
    }
    static instance = null;
    static getInstance(name,age){
        if(SinglePerson.instance)
            return SinglePerson.instance
        return SinglePerson.instance = new SinglePerson(...arguments)    
    }
}

let p1 = SinglePerson.getInstance("小明",18)
let p2 = SinglePerson.getInstance("小绿",17)
console.log(p1)
console.log(p2)