翻转二叉树，promise.all最佳实现

/**
 * 实现翻转二叉树
 * 例如
 *  a
 * / \
 * b c
 * 转为
 *  a
 * / |
 * c b
 */
const invertTree = function (root) {

    if (!root) {
        return
    }
    [root.left, root.right] = [root?.right, root?.left]
    invertTree(root.left)
    invertTree(root.right)
    return root
}


const ensure = (output, expect, message) => {
    if (JSON.stringify(output) === JSON.stringify(expect)) {
        console.log(`${message} ok`)
    } else {
        console.log(`${message} fail`)
    }
}

const test = function () {
    const input = {
        val: 1,
        left: {
            val: 2,
            left: {
                val: 3,
                left: null,
                right: null,
            },
            right: {
                val: 4,
                left: null,
                right: null,
            },
        },
        right: {
            val: 5,
            left: {
                val: 6,
                left: null,
                right: null,
            },
            right: {
                val: 7,
                left: null,
                right: null,
            },
        }
    }

    const expect = {
        val: 1,
        left: {
            val: 5,
            left: {
                val: 7,
                left: null,
                right: null,
            },
            right: {
                val: 6,
                left: null,
                right: null,
            },
        },
        right: {
            val: 2,
            left: {
                val: 4,
                left: null,
                right: null,
            },
            right: {
                val: 3,
                left: null,
                right: null,
            },
        }
    }

    const output = invertTree(input)
    ensure(output, expect, 'test')
}

// 输出 test ok表示测试成功
test()

// promise.all

Promise._all = function (promises) {

    return new Promise((r, j) => {
        const result = []
        promises.forEach((pro, index) => {
            Promise.resolve(pro).then(res => {
                result[index] = res
                if ( index === promises.length-1) {
                    r(result)
                }
            }).catch(err => {
                j(err)
            })
        })
    })
}

const ensure = function (output, expect, message) {
    if (JSON.stringify(output) === JSON.stringify(expect)) {
        console.log(`${message} ok`)
    } else {
        console.log(`${message} error`)
    }
}

const test1 = function () {
    Promise.all([
        new Promise(function (resolve, reject) {
            setTimeout(() => {
                resolve(1);
            }, 2000);
        }),
        Promise.resolve(2),
        3,
        Promise.resolve(4),
    ]).then(l => {
        console.log(l, 'lllll')
        let r = [1, 2, 3, 4]
        ensure(l, r, 'test 1')
    }).catch(err => {
        console.log(err)
    })
}

const test2 = function () {
    Promise._all([
        Promise.reject('error 1'),
    ]).catch(err => {
        ensure(err, 'error 1', 'test 2')
    })
}

const test = function () {
    test1()
    test2()
}

test()