【 工具函数 】拍平数组
<h4>拍平数组</h4>
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<p>最新的ES规范其实也加入了这个方法，功能是将一个数组压平，比如[1, 2, [3, [4, 5, [6, [7, 8]]]]], 会被处理成[1, 2, 3, 4, 5, 6, 7, 8]。</p>
<p>更近一步，实现可以压平指定深度的数组。</p>
<h3>代码：</h3>
<pre><code>// => 转变成一维数组
function flatten(list) {
if (list.length === 0) return [];
const head = list[0];
if (head instanceof Array) {
list[0] = flatten(head);
} else {
list[0] = [list[0]];
}
return list[0].concat(flatten(list.slice(1)));
}
//=> 指定深度的数组
function flattenDepth(list, n) {
if (list.length === 0) return [];
if (n === 0) return list;
const head = list[0];
if (head instanceof Array) {
list[0] = flattenDepth(head, n - 1);
} else {
list[0] = [list[0]];
}
return list[0].concat(flattenDepth(list.slice(1), n));
}
// test
const a = flatten([1, 2, [3, [4, 5, [6, [7, 8]]]]]);
console.log(a);
const b = flattenDepth([1, 2, [3, [4, 5, [6, [7, 8]]]]], 2);
console.log(b);
const c = flattenDepth([1, 2, [3, [4, 5, [6, [7, 8]]]]], Number.MAX_VALUE);
console.log(c);
</code></pre>