手写js ---- instanceof方法

递归方法：

function instanceof_(left,right){
    if(left.__proto__ === null){
        return false;
    }else{
        if(left.__proto__ === right.prototype){
            return true;
        }else{
            return instanceof_(left.__proto__,right);
        }
    }
}
function Person(name){
    this.name = name;
}

var david = new Person('david');
console.log(instanceof_(david,Person));

while循环（推荐这个，处理速度比闭包快多了）：

function instanceOf_(left,right) {
    let proto = left.__proto__;
    let prototype = right.prototype
    while(true) {
        if(proto == null) return false
        if(proto == prototype) return true
        proto = proto.__proto__;
    }
}
function Person(name){
    this.name = name;
}

var david = new Person('david');
console.log(instanceOf_(david,Person));