使用ES6

    1. Function.prototype.call2 = function (context, ...args) {
    2.   /// ...args 把剩余的参数都放到数组里面
    3.   var context = context || window
    4.   const fn = Symbol();
    5.   context.fn = this
    6.   let result = context.fn(...args)
    7.   delete context.fn
    8.   return result
    9. }
    1. Function.prototype.apply2 = function (context, arr) {
    2.   context = context || window
    3.   const fn = Symbol();
    4.   context.fn = this
    5.   let result = context.fn(...arr)
    6.   delete context.fn
    7.   return result
    8. }

    不使用ES6

    1. Function.prototype.call2 = function (context) {
    2.   context = context || window
    3.   context.fn = this
    4.   let args = []
    5.   for (let i = 1, len = arguments.length; i < len; i++) {
    6.     args.push('arguments['+i+']')
    7.   }
    8.   //这里使用eval，args 会自动调用 Array.toString() 这个方法。
    9.   let result = eval('context.fn('+args+')')
    10.   delete context.fn
    11.   return result
    12. }
    1. Function.prototype.apply2 = function (context, arr) {
    2.   context = context || window
    3.   context.fn = this
    4.   let result
    5.   if (!arr) {
    6.     result = context.fn()
    7.   } else {
    8.     let args = []
    9.     for (let i = 0, len = arr.length; i < len; i++) {
    10.       args.push('arr[' + i + ']')
    11.     }
    12.     result = eval('context.fn(' + args + ')')
    13.   }
    15.   delete context.fn
    16.   return result
    17. }