创建一个具有相同元素重复多次的数组 [英] Create an array with same element repeated multiple times

问题描述

在Python中， [2] 是一个列表，下面的代码给出了这个输出：

In Python, where [2] is a list, the following code gives this output:

[2] * 5 # Outputs: [2,2,2,2,2]

在JavaScript中使用数组是否存在一种简单的方法？

Does there exist an easy way to do this with an array in JavaScript?

我写了以下函数来做它，但有更短或更好的东西吗？

I wrote the following function to do it, but is there something shorter or better?

var repeatelem = function(elem, n){
    // returns an array with element elem repeated n times.
    var arr = [];

    for (var i = 0; i <= n; i++) {
        arr = arr.concat(elem);
    };

    return arr;
};

推荐答案

你可以这样做：

function fillArray(value, len) {
  if (len == 0) return [];
  var a = [value];
  while (a.length * 2 <= len) a = a.concat(a);
  if (a.length < len) a = a.concat(a.slice(0, len - a.length));
  return a;
}

它在每次迭代中使数组加倍，因此它可以创建一个非常大的数组迭代次数很少。

It doubles the array in each iteration, so it can create a really large array with few iterations.

注意：你也可以通过 push <来改善你的功能/ code>而不是 concat ，因为 concat 将在每次迭代时创建一个新数组。像这样（仅作为如何使用数组的示例）：

Note: You can also improve your function a lot by using push instead of concat, as concat will create a new array each iteration. Like this (shown just as an example of how you can work with arrays):

function fillArray(value, len) {
  var arr = [];
  for (var i = 0; i < len; i++) {
    arr.push(value);
  }
  return arr;
}

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