如何从对象中深度删除空值，空对象和空数组

Question

I have an object that looks like this:

var myObject = { a: { b: [{}], c: [{}, {d: 2}], e: 2, f: {} }, g:{}, h:[], i: [null, 2] }

I want to remove null values and and empty objects (array and objects) so that it looks like:

{ a: {c: [ {d: 2} ], e: 2 }, i: [ 2 ] }

The function should remove null values, empty objects and empty arrays. Any elegant way to do it ?

Answer 1

Here is a function that clean the object recursively. It will loop deeply through all the properties and remove null values, null arrays and null objects:

cleanUpObject(jsonObject: object): object {

    Object.keys(jsonObject).forEach(function (key, index) {
        const currentObj = jsonObject[key]

        if (_.isNull(currentObj)) {
            delete jsonObject[key]
        } else if (_.isObject(currentObj)) {
            if (_.isArray(currentObj)) {
                if (!currentObj.length) {
                    delete jsonObject[key]
                } else {
                    const cleanupArrayObj = []
                    for (const obj of currentObj) {
                        if (!_.isNull(obj)) {
                            const cleanObj = this.cleanUpJson(obj)
                            if (!_.isEmpty(cleanObj)) {
                                cleanupArrayObj.push(cleanObj)
                            }
                        }
                    }
                    if (!cleanupArrayObj.length) {
                        delete jsonObject[key]
                    } else {
                        jsonObject[key] = cleanupArrayObj
                    }
                }
            } else {
                if (_.isEmpty(Object.keys(jsonObject[key]))) {
                    delete jsonObject[key]
                } else {
                    jsonObject[key] = this.cleanUpJson(currentObj)

                    if (_.isEmpty(Object.keys(jsonObject[key]))) {
                        delete jsonObject[key]
                    }
                }
            }
        }
    }, this)

    return jsonObject
}

Answer 2

To reduce repetitive code, one option is to define a function (let's call it itemToBool ) that can determine whether a generic value passed to it is truthy, or recursively truthy somewhere , should the value be an array or object. Then, in the function that gets passed the original object (or, gets recursively passed an object or array), you can call that itemToBool function whenever there's a value to validate.

In the case of arrays, map by itemToBool and then filter by Boolean. In the case of objects, reduce the entries of the object into another object: pass each value of the object through itemToBool to recursively transform it (in case the value is an array or object), and if the transformed value has any keys (or is a truthy primitive), assign it to the accumulator. No need to depend a library:

 var myObject = { a: { b: [{}], c: [{}, { d: 2 }], e: 2, f: {} }, g: {}, h: [], i: [null, 2] }; // Returns a falsey value if the item is falsey, // or if the deep cleaned array or object is empty: const itemToBool = item => { if (typeof item !== 'object' || item === null) return item; const cleanedItem = clean(item); return Object.keys(cleanedItem).length !== 0 && cleanedItem; }; const clean = obj => { if (Array.isArray(obj)) { const newArr = obj.map(itemToBool).filter(Boolean); return newArr.length && newArr; } const newObj = Object.entries(obj).reduce((a, [key, val]) => { const newVal = itemToBool(val); if (newVal) a[key] = newVal; return a; }, {}); return Object.keys(newObj).length > 0 && newObj; }; console.log(clean(myObject)); 

Hmm... you also might abstract the check of the number of keys into a function as well:

 var myObject={a:{b:[{}],c:[{},{d:2}],e:2,f:{}},g:{},h:[],i:[null,2]} // Returns the object / array if it has at least one key, else returns false: const validObj = obj => Object.keys(obj).length && obj; const itemToBool = item => ( typeof item !== 'object' || item === null ? item : validObj(clean(item)) ); const clean = obj => validObj( Array.isArray(obj) ? obj.map(itemToBool).filter(Boolean) : Object.entries(obj).reduce((a, [key, val]) => { const newVal = itemToBool(val); if (newVal) a[key] = newVal; return a; }, {}) ); console.log(clean(myObject)); 

Answer 3

We don't know what you mean by clean , but from what I understand, you want to remove all null and empty values. This algorithm is straight-forward: recursively check for and remove any empty / null values (which are recursively checked).

 function clean(obj) { // clean array if (Array.isArray(obj)) { for (let i=0; i<obj.length; i++) { if (isNothing(obj[i])) obj.splice(i, 1); // remove value if falsy else if (typeof obj[i] === 'object') clean(obj[i]); // recurse if it's a truthy object } // clean other object } else { for (let prop in obj) { if (!obj.hasOwnProperty(prop)) continue; if (isNothing(obj[prop])) delete obj[prop]; // remove value if falsy else if (typeof obj[prop] === 'object') clean(obj[prop]); // recurse if it's a truthy object } } } // Recursively check for populated or nonnull content. If none found, return `true`. Recursive so [{}] will be treated as empty. function isNothing(item) { // null / undefined if (item == null) return true; // deep object falsiness if (typeof item === 'object') { if (Array.isArray(item)) { // array -> check for populated/nonnull value for (let i=0; i<item.length; i++) { if (!isNothing(item[i])) return false; } return true; } // other object -> check for populated/nonnull value for (let prop in item) { if (!item.hasOwnProperty(prop)) continue; if (!isNothing(item[prop])) return false; } return true; } return false; } var myObject = { a: { b: [{}], c: [{}, {d: 2}], e: 2, f: {} }, g:{}, h:[], i: [null, 2] }; console.log("Before: " + JSON.stringify(myObject)); clean(myObject); console.log("After: " + JSON.stringify(myObject));