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27 lines (26 loc) · 944 Bytes
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/* eslint-disable no-proto */
/*
* Author : OBKoro1
* Date : 2021-07-30 15:02:10
* LastEditors : OBKoro1 1677593011@qq.com
* LastEditTime : 2024-04-21 14:29:06
* FilePath : /web-basics/src/js/intanceof/intanceof.js
* description : instanceOf实现原理
* koroFileheader VSCode插件
* Copyright (c) 2021 by OBKoro1, All Rights Reserved.
*/
// 作用：一个对象是否在另一个对象的原型链上
// 思路：左边变量的原型链上 有 右边变量的原型， 说明左边对象是继承右边对象的。
function instanceOf(left, right) {
let leftValue = left.__proto__
const rightValue = right.prototype
while (true) {
if (leftValue === null) {
return false // 左边变量的原型链上没找到
}
if (leftValue === rightValue) {
return true // 右边变量的原型在左边变量的原型链上
}
leftValue = leftValue.__proto__ // 找下层原型
}
}