Filtering object properties based on value

Question

Is there some elegant way of filtering out falsey properties from this object with lodash/underscore? Similar to how _.compact(array) removes falsey elements from arrays

so from

{
  propA: true,
  propB: true,
  propC: false,
  propD: true,
}

returning

{
  propA: true,
  propB: true,
  propD: true,
}

Answer 1

Here are two vanilla javascript options:

A.: Iterate over the object's keys and delete those having a falsey value.

var obj = {
  propA: true,
  propB: true,
  propC: false,
  propD: true,
};

Object.keys(obj).forEach(key => {
  if (!obj[key]) delete obj[key];
});

console.log(obj);

_{See Object.keys() and Array.prototype.forEach()}

B.: Iterate over the object's keys and add truthy values to a new object.

var obj = {
  propA: true,
  propB: true,
  propC: false,
  propD: true,
};

var filteredObj = Object.keys(obj).reduce((p, c) => {    
  if (obj[c]) p[c] = obj[c];
  return p;
}, {});

console.log(filteredObj);

_{See Object.keys() and Array.prototype.reduce()}

Answer 2

Lodash 4.0

Lodash 4.0 has _.pick, which takes an array of properties, and _.pickBy which takes a function as an argument and returns an object only containing the keys for which that function returns truthy which is what we want here, so it'd be:

filtered = _.pickBy(obj, function(value, key) {return value;})

Or, since _.pickBy defaults to using _.identity as it's second argument, (and that's essentially what we've written above,) it can just be written as:

filtered = _.pickBy(obj);

Underscore or Lodash prior to version 4.0

In underscore and old versions of lodash, there's just a single _.pick, which has both behaviors of _.pick and _.pickWith from v4. So you can do:

filtered = _.pick(obj, function(value, key) {return value;})

Or more succinctly:

filtered = _.pick(obj, _.identity)

Answer 3

As partially mentioned in a comment, ES6 provided Object.entries() and in 2019 Object.fromEntries().

Allowing:

Object.fromEntries(Object.entries(obj).filter(([key, value]) => ...))

Ex:

const obj = {
  a: 12,
  b: 123,
};

const filteredObj = Object.fromEntries(
  Object.entries(obj).filter(
    ([_, value]) => value > 100
  )
);

console.log(filteredObj);
// {b: 123}

Answer 4

Unfortunately I cannot direclty comment on the posts above yet, so I create this extra post.

Since Lodash v4 the functionality described above has been moved to _.pickBy. With _.identity as default you could also change your code to:

var filtered = _.pickBy(obj);

See this JSBin for a working example.

Answer 5

If you're using lodash, I'd recommend something like this:

var object = {
    propA: true,
    propB: true,
    propC: false,
    propD: true,
};

_.pick(object, _.identity);
// →
// {
//   propA: true,
//   propB: true,
//   propD: true
// }

The pick() function generates a new object that includes properties that the callback returns truthy for. So we can just use the identity() function as the callback, since it'll just return each property value.

Answer 6

From lodash 4, we can use pickBy() to get only the value equal to true.

const active = _.keys(_.pickBy(object));

Answer 7

let temp = {
  propA: true,
  propB: true,
  propC: false,
  propD: true,
}

let obj = {}
for(x in temp){
   if(temp[x] == true){
     obj[x] = temp[x]
   }
}

console.log(obj)

Using for-in loop we can achieve it something like this.

Answer 8

Another approach

const objFilter = (obj, condition) => {
    let newObj = {}
    for (const [key, value] of Object.entries(obj)) {
        if (condition(value)) {
            newObj = { ...newObj, [key]: value }
        }
    }
    return newObj
}

Fire like this:

const newData = objFilter(oldData, (value) => value.marked === false)