Array.prototype.flat原理实现

将深度嵌套的数组，扁平化

Array.prototype.flat = function (n = 1) {
    let current = this;
    let count = 0;
    
    // 校验数组为空/ 扁平参数0
    if (!current.length || n == 0)  return current;
    
    // 捕获数组元素错误 [1, x];
    try {
        // 循环扁平
        while (count++ < n) {
            // 判断上一轮扁平化后的数组元素，都非数组
            if (!current.some(Array.isArray)) return current;
            // 不断把拉平的结果赋值给current，更新后返还
            current = current.reduce((prev, next) => prev.concat(next), []);
        }
    } catch(error) {
        throw error;
    }
    
    // 返回结果
    return current;
}

验证

let arr = [1, [1, [3, [4, [5]]]]];
arr.flat("tom");
//[1, [1, [3, [4, [5]]]]]
arr.flat();
//[1, [1, [3, [4, [5]]]]]
arr.flat(1);
//[1, 1, [3, [4, [5]]]]
arr.flat(Infinity);
//[1, 1, 3, 4, 5]