2823-DeepObjectFilter.js

// 2823. Deep Object Filter
// Given an object or an array obj and a function fn, return a filtered object or array filteredObject. 
// Function deepFilter should perform a deep filter operation on the obj. 
// The deep filter operation should remove properties for which the output of the filter function fn is false, as well as any empty objects or arrays that remain after the keys have been removed.

// If the deep filter operation results in an empty object or array, 
// with no remaining properties, deepFilter should return undefined to indicate that there is no valid data left in the filteredObject.

// Example 1:
// Input: 
// obj = [-5, -4, -3, -2, -1, 0, 1], 
// fn = (x) => x > 0
// Output: [1]
// Explanation: All values that were not greater than 0 were removed.

// Example 2:
// Input: 
// obj = {"a": 1, "b": "2", "c": 3, "d": "4", "e": 5, "f": 6, "g": {"a": 1}}, 
// fn = (x) => typeof x === "string"
// Output: {"b":"2","d":"4"}
// Explanation: 
//     All keys with values that were not a string were removed. 
//     When the object keys were removed during the filtering process, any resulting empty objects were also removed.

// Example 3:
// Input: 
// obj = [-1, [-1, -1, 5, -1, 10], -1, [-1], [-5]], 
// fn = (x) => x > 0
// Output: [[5,10]]
// Explanation: 
//     All values that were not greater than 0 were removed. 
//     When the values were removed during the filtering process, any resulting empty arrays were also removed.

// Example 4:
// Input: 
// obj = [[[[5]]]], 
// fn = (x) => Array.isArray(x)
// Output: undefined
 

// Constraints:
//         fn is a function that returns a boolean value
//         obj is a valid JSON object or array
//         2 <= JSON.stringify(obj).length <= 10^5

/**
 * @param {Object|Array} obj
 * @param {Function} fn
 * @return {Object|Array|undefined}
 */
var deepFilter = function(obj, fn) {
    // 传入的为数组 递归循环
    if (Array.isArray(obj)) {
        const res = []
        for (let item of obj) {
            const cb = deepFilter(item, fn)
            // 结果不为 undefined 放入返回结果中
            if (cb !== undefined) res.push(cb)
        }
        return res.length ? res : undefined
    }
    // 处理对象
    if (typeof obj === 'object') {
        if (obj === null) return fn(obj) ? null : undefined
        const res = {}
        let ok = false
        for (let key of Object.keys(obj)) {
            const cb = deepFilter(obj[key], fn)
            if (cb !== undefined) {
                ok = true
                res[key] = cb
            }
        }
        return ok ? res : undefined
    }
    // 处理不需要递归
    return fn(obj) ? obj : undefined
};

// Example 1:
console.log(
    deepFilter(
        [-5, -4, -3, -2, -1, 0, 1],
        (x) => x > 0
    )
) // [1]
// Example 2:
console.log(
    deepFilter(
        {"a": 1, "b": "2", "c": 3, "d": "4", "e": 5, "f": 6, "g": {"a": 1}},
        (x) => typeof x === "string"
    ) 
) // {"b":"2","d":"4"}
// Example 3:
console.log(
    deepFilter(
        [-1, [-1, -1, 5, -1, 10], -1, [-1], [-5]],
        (x) => x > 0
    )
) // [[5,10]]
// Example 4:
console.log(
    deepFilter(
        [[[[5]]]],
        (x) => Array.isArray(x)
    )
) // undefined
// Input: 
// obj = [[[[5]]]], 
// fn = (x) => Array.isArray(x)
// Output: undefined