How to deep remove falsey values and empty objects from an object using lodash

Question

How to deep remove all falsey values and empty objects using lodash ?

f.e. I want my object :

{ a:undefined, b:2, c:4, d:undefined , e:{ f:{} , g:null } }

to become:

{ b:2, c:4 };

So it will recursively go through all objects? Also {} is not falsy. — evolutionxbox
– evolutionxbox, Commented Oct 20, 2020 at 13:13
Would a for .. of loop not work here? Then use an if and delete false properties? — evolutionxbox
– evolutionxbox, Commented Oct 20, 2020 at 13:15
please add your attempt. do you want to get a new object or only delete unwanted properties? do you have arrays as well? — Nina Scholz
– Nina Scholz, Commented Oct 20, 2020 at 13:51

Marc · Accepted Answer · 2020-10-20 14:04:57Z

2

var test = {
  a: undefined,
  b: 2,
  c: 4,
  d: undefined,
  e: {
    f: {},
    g: null
  }
};

function clean(obj) {
  for (var propName in obj) {
    if (_.isObject(obj[propName])) {
      clean(obj[propName]);
    }
    if (obj[propName] === null || obj[propName] === undefined || _.isObject(obj[propName]) && _.isEmpty(obj[propName])) {
      delete obj[propName];
    }
  }
}

clean(test);
console.log(test);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.20/lodash.min.js"></script>

edited Oct 20, 2020 at 14:04

Marc

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answered Oct 20, 2020 at 13:51

MWO

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Comments

Nina Scholz · Accepted Answer · 2020-10-20 14:13:43Z

0

You could get the properties to delete and get a clean object. This approach mutates to original object.

function clean(value) {
    if (value === null || value === undefined) return true;
    if (typeof value !== 'object') return false;
    if (Array.isArray(value)) {
        let i = value.length;
        while (i--) if (clean(value[i])) value.splice(i, 1);
        return !value.length;
    }
    Object
        .keys(value)
        .filter(k => clean(value[k]))
        .forEach(Reflect.deleteProperty.bind(null, value));

    return !Object.keys(value).length;
}

const 
    object = { a: undefined, b: 2, c: 4, d: undefined, e: { f: {}, g: null } , h: [], i: [1, []], j: [[[], []]] };

clean(object);

console.log(object);

edited Oct 20, 2020 at 14:13

answered Oct 20, 2020 at 14:07

Nina Scholz

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1 Comment

Nina Scholz Over a year ago

needless to ask why ... why?

3limin4t0r · Accepted Answer · 2020-10-20 15:45:38Z

The question is pretty vague and doesn't specify whether the original structure may or may not be mutated. There is also nothing in there about arrays.

This answer assumes that you don't want to mutate the original data structure and that "deep" also means to go through all array elements. If the object or array results in an empty instance the corresponding key will be removed.

function deepCompact(collection) {
  const add = _.isArray(collection)
            ? (collection, key, value) => collection.push(value)
            : (collection, key, value) => collection[key] = value;
  
  return _.transform(collection, (collection, value, key) => {
    if (_.isObject(value)) {
      value = deepCompact(value);
      if (_.isEmpty(value)) return;
    } else {
      if (!value) return;
    }
    add(collection, key, value);
  });
}

const data1 = {a: undefined, b: 2, c: 4, d: undefined, e: {f: {} , g: null}};
console.log(deepCompact(data1));
const data2 = [{a: 0, b: 2}, false, {c: [{d: null}]}, {e: [{f: 1}]}];
console.log(deepCompact(data2));

<script src="https://cdn.jsdelivr.net/npm/[email protected]/lodash.min.js"></script>

transform is comparable to reduce, however the first callback parameter is locked to the provided or default accumulator. This means you don't have to return the accumulator from the callback. The default accumulator of transform also differs from reduce. reduce uses the first element as the initial value, whereas transform uses a new object with the same prototype as the provided collection as the default value.

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