Array.flat原理实现

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Array.flat实现

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// input [1, 2, [3, 4, [5, 6, 7]], 8] -> output [1, 2, 3, 4, 5, 6, 7, 8];
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interface Array<T> {
    flatInfinity(): T[];
    flat(n?: number): T[];
}
Array.prototype.flatInfinity = function() {
    const stack = [...this];
    const value = [];
    while (stack.length) {
        const next = stack.pop();
        if (Array.isArray(next)) {
            stack.push(...next);
        } else {
            value.push(next);
        }
    }
    return value.reverse();
};
Array.prototype.flat = function(n = 1) {
    return baseFlatten(this, n, []);
};
baseFlatternlodash.js
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/**
 * 将数组拉平
 * @param {Array} array 需要拉平数组
 * @param {number} depth 数组的深度
 * @param {Array} result 初始化将要返回的数组
 * @returns {Array} 返回扁平后的数组
 */
function baseFlatten(array, depth, result) {
    result || (result = []);
    if (array == null) {
        return result;
    }
    for (const value of array) {
        if (depth > 0 && Array.isArray(value)) {
            if (depth > 1) {
                baseFlatten(value, depth - 1, result);
            } else {
                result.push(...value);
            }
        } else {
            result[result.length] = value;
        }
    }
    return result;
}