如果不传入参数，默认指向window/**
* 实现一个call方法
*/
Function.prototype.myCall = function (context) {
context = context ? Object(context) : window;
context.fn = this; // 获取调用call的函数
let args = [];
for (let i = 1, len = arguments.length; i < len; i++) { args.push(arguments[i]); }
let result = context.fn(...args);
return result; }
var value = 'global';
var foo = {
value: 1
};
var bar = function (name, age) {
console.log(this.value);
return {
value: this.value,
name,
age }}
bar.myCall(null);
console.log(bar.myCall(foo, '铁拐李', 18));
