done[白板]instanceof

A instanceof B, A是否在B的原型链上

const new_instanceof = function (instance, constructor) {
    let instance_proto = instance.__proto__;
    let constructor_proto = constructor.prototype;
    while(true) {
        // 找到终点返回false
       if (instance_proto === null) {return false};
       // 找到返回true
       if (instance_proto === constructor_proto) {return true};
        // 当实例与构造函数原型不相同, 沿着原型链继续向上查找
        instance_proto = instance_proto.__proto__;
    }
}
console.log([] instanceof Array)   // true
console.log(new_instanceof([], Array))  // true