JS 面试题

1. 使以下代码正常运行

const a = [1, 2, 3, 4, 5]; 
a.multiply(); 
console.log(a); // [1, 2, 3, 4, 5, 1, 4, 9, 16, 25]
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var a = [1, 2, 3, 4, 5];
Array.prototype.multiply = function(arr) {
  var temp = this.map(item => item * item);
  return a.concat(temp);
}