javascript - 在 JavaScript 中调用不带参数的 concat 有什么作用

Question

不带参数调用 concat 的要点/结果是什么？例如

代码:

 var board = [
  false, false, false, false,
  false, false, false, false
];
board = board.concat();

Answer 1

Concat function用于在 javascript 中连接两个数组。

例如:

a = [1,2,3]
b = [4,5]

a = a.concat(b); // a becomes [1,2,3,4,5]

编辑

使用不带参数的concat 可用于复制数组。例如:

var a = [1,2,3];
var b = a.concat();
b.push(4);

// a is [1,2,3] and b is [1,2,3,4]

从 MDN concat 源阅读此内容

concat does not alter this or any of the arrays provided as arguments but instead returns a shallow copy that contains copies of the same elements combined from the original arrays. Elements of the original arrays are copied into the new array