[Javascript] Write .call()

Function.apply.myCall = function (ctx, ...args) {
  ctx = ctx === null || ctx === undefined ? globalThis : Object(ctx);
  const fn = this;
  const key = Sybmol("fn");
  // we don't want user can see [Sybmol("key")] in Function prototype
  // that's why we use Object.defineProperty to make it non-enumerable
  Object.defineProperty(ctx, key, {
    enumarable: false,
    value: fn,
  });
  const r = ctx[key](...args);
  return r;
};

function method(a, b) {
  console.log("args:", a, b);
  console.log("this:", this);
}

method.myCall(1, 2, 3); // this: [Number: 1]
method.myCall(null, 2, 3); // this: [global]
method.myCall(undefined, 2, 3); // this: [global]
method.myCall({}, 2, 3); // this: {}

 

posted @   Zhentiw  阅读(5)  评论(0编辑  收藏  举报
相关博文:
阅读排行:
· 阿里最新开源QwQ-32B,效果媲美deepseek-r1满血版,部署成本又又又降低了!
· Manus重磅发布:全球首款通用AI代理技术深度解析与实战指南
· 开源Multi-agent AI智能体框架aevatar.ai,欢迎大家贡献代码
· 被坑几百块钱后,我竟然真的恢复了删除的微信聊天记录!
· AI技术革命,工作效率10个最佳AI工具
历史上的今天:
2023-10-18 [Compose] Async programming: Thunks
2022-10-18 [RxJS] mergeAll - mergeMap
2022-10-18 [RxJS] Use finalize for side effects on completion
2022-10-18 [!Typescript] Tips: Access deeper parts of objects and arrays
2022-10-18 [Typescript] 56. Medium - Flip Arguments
2022-10-18 [Typescript] 55. Medium - Reverse
2022-10-18 [Jest] Note
点击右上角即可分享
微信分享提示