call实现

Function.prototype.myCall = function(obj) {  //靠(call)，帮(绑)甜（添）姐（解）执单（删）反（返）
  let context = obj || window; //1.绑定全局环境             绑
  context.fn = this; //2.添加临时属性存储调用函数             添
  let args = [...arguments].slice(1) //3.解析参数          解
  let result = context.fn(...args); //4.执行函数，取得结果   执
  delete context.fn; //5.删除临时属性                       删
  return result //6.返回执行结果                            返
}

let obj = {
  name: 'xx'
};

function showName(...args) {
  console.log(`name: ${this.name}, args: ${args}`)
}

showName.myCall(obj,34, 35, 36)