如何在javascript中展平嵌套数组? [英] How to flatten nested array in javascript?

问题描述

正如我们所知，使用 reduce()[[0, 1], [2, 3], [4, 5]]>

As we know, to flatten the array [[0, 1], [2, 3], [4, 5]] by using the method reduce()

var flattened = [[0, 1], [2, 3], [4, 5]].reduce(function(a, b) {
  return a.concat(b);
});

那么如何将这个数组[[[0], [1]], [[2], [3]], [[4], [5]]] 扁平化为[0, 1, 2, 3, 4, 5]?

So how to flatten this array [[[0], [1]], [[2], [3]], [[4], [5]]] to [0, 1, 2, 3, 4, 5]?

推荐答案

这是递归的替代方案 (在此处查看 jsfiddle) 并且应该接受避免堆栈溢出的任何深度级别.

This is an alternative to recursion (see jsfiddle here) and should accept any level of depth which avoids stack overflow.

var array = [[0, 1], [2, 3], [4, 5, [6, 7, [8, [9, 10]]]]];
console.log(flatten(array), array); // does not mutate array
console.log(flatten(array, true), array); // array is now empty

// This is done in a linear time O(n) without recursion
// memory complexity is O(1) or O(n) if mutable param is set to false
function flatten(array, mutable) {
    var toString = Object.prototype.toString;
    var arrayTypeStr = '[object Array]';
    
    var result = [];
    var nodes = (mutable && array) || array.slice();
    var node;

    if (!array.length) {
        return result;
    }

    node = nodes.pop();
    
    do {
        if (toString.call(node) === arrayTypeStr) {
            nodes.push.apply(nodes, node);
        } else {
            result.push(node);
        }
    } while (nodes.length && (node = nodes.pop()) !== undefined);

    result.reverse(); // we reverse result to restore the original order
    return result;
}

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