手写源码-实现 flat 拍平数组

1. forEach 循环实现

const animals = ["🐷", ["🐶", "🐂"], ["🐎", ["🐑", ["🐲"]], "🐛"]];
Array.prototype.myFlat = function (number = 1) {
    const array = this;
    const res = [];
    const getFlatArray = (array, _number) => {
        if (_number < 0) {
            res.push(array);
            return;
        }
        array.forEach((item) => {
        if (Object.prototype.toString.call(item) == "[object Array]") {
            getFlatArray(item,  _number - 1);
        } else {
            res.push(item);
        }
        });
    };
    getFlatArray(array, number);
    return res;
};

console.log(
  animals.myFlat(Infinity)
);
// ['🐷', '🐶', '🐂', '🐎', '🐑', '🐲', '🐛']

2. 通过 concat 实现拍平
   通过 arguments.callee 实现递归（只能在严格模式下使用）

const animals = ["🐷", ["🐶", "🐂"], ["🐎", ["🐑", ["🐲"]], "🐛"]];
Array.prototype.myFlat = function () {
    const array = this;
    let res = [];
    array.forEach((item) => {
        if (Array.isArray(item)) {
            res = res.concat(arguments.callee(item));
        } else {
            res = res.concat(item);
        }
    });
    return res;
};

console.log(animals.myFlat());

3. 通过 reduce 实现，并可通过参数控制拍平层数。

const animals = ["🐷", ["🐶", "🐂"], ["🐎", ["🐑", ["🐲", [1]]], "🐛"]];
Array.prototype.myFlat = function (num=1) {
    const array = this;
    return num > 0
        ? array.reduce((acc, cur) => Array.isArray(cur) ? acc.concat(cur.myFlat(num - 1)) : acc.concat(cur),[])
        : array;
};

console.log(animals.myFlat());

4. 通过 generator 实现。

const animals = ["🐷", ["🐶", "🐂"], ["🐎", ["🐑", ["🐲", [1]]], "🐛"]];
Array.prototype.myFlat = function* (num = 1) {
    const array = this;
    for (let item of array) {
        if (num > 0 && Array.isArray(item)) {
            yield* item.myFlat(num - 1);
        } else {
            yield item;
        }
    }
};