手写 instanceof。
时间: 2023-09-02 18:11:13 浏览: 53
function myInstanceOf(left, right) {
let rightVal = right.prototype;
let leftVal = left.__proto__;
while (true) {
if (leftVal === null) {
return false;
}
if (leftVal === rightVal) {
return true;
}
leftVal = leftVal.__proto__;
}
}
测试用例:
function Test() {}
let test = new Test();
console.log(myInstanceOf(test, Test));
结果: true
instanceof的实现原理是只要右边变量的prototype在左边变量的原型链上即可,即左边的变量能在原型链上找到右边变量的prototype。在查找的过程中,会遍历左边变量的原型链,直到找到右边变量的prototype,如果查找失败,则会返回false。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
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