Remove empty objects from an object

Question

I am trying to remove empty objects inside an object, here is an example with the expected output:

var object = {
    a: {
        b: 1,
        c: {
            a: 1,
            d: {},
            e: {
              f: {} 
            }
        }
    },
    b: {}
}


var expectedResult = {
    a: {
        b: 1,
        c: {
            a: 1,
        }
    }
}

I tried using some examples from other StackOverflow questions, however those are just for one level objects.

Answer 1

Basic function that removes empty objects

First start with a function that only works with a single level of nesting.

This function removes all properties that reference an empty object:

function clearEmpties(o) {
  for (var k in o) {
    if (!o[k] || typeof o[k] !== "object") {
      continue // If null or not an object, skip to the next iteration
    }

    // The property is an object
    if (Object.keys(o[k]).length === 0) {
      delete o[k]; // The object had no properties, so delete that property
    }
    return o;
  }
}

---

Handling nested objects using recursion

Now you want to make it recursive so that it will operate on nested objects. So we already have tested if o[k] is an object, and we've tested if there are properties, so if there are, we simply call the function again with that nested object.

function clearEmpties(o) {
  for (var k in o) {
    if (!o[k] || typeof o[k] !== "object") {
      continue // If null or not an object, skip to the next iteration
    }

    // The property is an object
    clearEmpties(o[k]); // <-- Make a recursive call on the nested object
    if (Object.keys(o[k]).length === 0) {
      delete o[k]; // The object had no properties, so delete that property
    }
  }
    return o;
}

So just as the original call to clearEmpties removes properties of the given object that reference an empty object, likewise the recursive call will do the same for the nested objects.

---

Live demo:

var object = {
  a: {
    b: 1,
    c: {
      a: 1,
      d: {},
      e: { // will need to be removed after f has been removed
         f: {} 
      }
    }
  },

  b: {}
};

clearEmpties(object);
console.log(object);

function clearEmpties(o) {
  for (var k in o) {
    if (!o[k] || typeof o[k] !== "object") {
      continue
    }

    clearEmpties(o[k]);
    if (Object.keys(o[k]).length === 0) {
      delete o[k];
    }
  }
  return o;
}

---

Short version using Underscore and functional style

function clearEmpties(o) {
  if (_.isFunction(o) || !_.isObject(o)) return o;
  return _.chain(o)
    .mapObject(clearEmpties)
    .pick(p => !(_.isObject(p) && _.isEmpty(p)))
    .value();
}

Short version using lodash and functional style - works with treeshaking

import { isFunction, isObject, isEmpty, isArray, isPlainObject, fromPairs } from "lodash-es";

const removeEmtpyObjects = (o) => {
    if (isFunction(o) || !isPlainObject(o)) return o;

    if (isArray(o)) return o.map(removeEmtpyObjects);

    return fromPairs(
        Object.entries(o)
            .map(([k, v]) => [k, removeEmtpyObjects(v)])
            .filter(([k, v]) => !(v == null || (isObject(v) && isEmpty(v))))
    );
};

Answer 2

I had this same problem and with the addition that my object may contain arrays with empty elements that need to be removed as well.

I ended up with this quick and dirty solution.

If you want to define what "empty" means to you, I also added a different function. In my case, I also needed empty strings.

  function isEmpty(obj) {
        if (obj === '' || obj === null || JSON.stringify(obj) === '{}' || JSON.stringify(obj) === '[]' || (obj) === undefined || (obj) === {}) {
            return true
        } else {
            return false
        }
    }
    function removeEmpty(o) {
        if (typeof o !== "object") {
            return o;
        }
        let oKeys = Object.keys(o)
        for (let j = 0; j < oKeys.length; j++) {
            let p = oKeys[j]
            switch (typeof (o[p])) {
                case 'object':
                    if (Array.isArray(o[p])) {
                        for (let i = 0; i < o[p].length; i++) {
                            o[p][i] = removeEmpty(o[p][i])
                            if (isEmpty(o[p][i])) {
                                o[p].splice(i, 1)
                                i--
                            }
                        }
                        if (o[p].length === 0) {
                            if (Array.isArray(o)) {
                                o.splice(parseInt(p), 1)
                                j--
                            } else {
                                delete o[p]
                            }
                        }
                    } else {
                        if (isEmpty(o[p])) {
                            delete o[p]
                        } else {
                            o[p] = removeEmpty(o[p])
                            if (isEmpty(o[p])) {
                                delete o[p]
                            }
                        }
                    }
                    break
                default:
                    if (isEmpty(o[p])) {
                        delete o[p]
                    }
                    break
            }
    
        }
        if (Object.keys(o).length === 0) {
            return
        }
        return o
    }

Input:

var a = {
b: 1,
c: {
    d: [1, [[], [], [[[1], []]]], [2, [[], [[]]]], [], [[]]]
},
e: {
    f: [{}, { g: 1 }]
},
h: {
    i: { j: { k: undefined, l: null, m: { n: "", o: 1 } } }
},
p: { q: { r: 1 } }
}
removeEmpty(a)

Output:

   {
    "b": 1,
    "c": {
        "d": [1, [[[[1]]]], [2]]
    },
    "e": {
        "f": [{"g": 1}]
    },
    "h": {
        "i": {
            "j": {
                "m": {
                    "o": 1
                }
            }
        }
    },
    "p": {
        "q": {
            "r": 1
        }
    }
}