使以下代码正常运行

[Rashomon511]

let a = [1,2,3,4,5] a.multiply() console.log(a) // [1, 2, 3, 4, 5, 1, 4, 9, 16, 25]

    Object.prototype.multiply = function(){
      let arr = this;
      a = arr.concat(arr.map(item => item * item))
    }