How to check whether there is difference in two array in javascript?

Question

There is a similar question on StackOverflow here in this question we need to get the difference in the array.

But I just want true or false. I don't need the different array.

I tried it like this:

groups = [{id: 1, name: "check 1"}, {id: 2, name: "check 2"}]

checkedgroups = [{id: 1, name: "check 1"}, {id: 2, name: "check 2"}, {id: 3, name: "check 3"}]

My solution: _.differenceBy(groups, checkedGroups, 'id').length

Please post your `differenceBy` function. I suspect the error is caused by something in there. — JoshG, Jan 24 '19 at 06:37
If you need length difference then why no `checkedgroups.length - groups.length` — brk, Jan 24 '19 at 06:38
@brk i need to check the difference by considering id as common between these two aray. — vikas95prasad, Jan 24 '19 at 06:39
@vikas95prasad There is no built-in `differenceBy` function in JavaScript. — JoshG, Jan 24 '19 at 06:40
Okay, then how can I use lodash ```differenceBy``` function? — vikas95prasad, Jan 24 '19 at 06:43
You say you want a `true` or `false` as your output, but then at the bottom of your question, you say you expect a number representing the length as the output? Which one is it? — Nick Parsons, Jan 24 '19 at 06:43
Possible duplicate of [How to get the difference between two arrays in Javascript?](https://stackoverflow.com/questions/1187518/how-to-get-the-difference-between-two-arrays-in-javascript) — Varun Sukheja, Jan 24 '19 at 06:44

score 1 · Answer 1 · edited Jan 24 '19 at 06:55

You can try different arrays and check the output. It uses a filter function. If the elements are not equal the array returned by filter is empty. Otherwise array of length of the original array is returned.

var a = ['a', 'b'];
var b = ['a', 'b'];

function w(a, b) {
  if (a.length != b.length)
    return false;
  else {
    var k = a.filter((e) => b[a.indexOf(e)] == e)
    if (k.length == 0)
      return false;
    else if (k.length == a.length)
      return true
  }
}
console.log(w(a, b))

Mamun · Answer 2 · 2019-01-25T04:21:33.887

You can get the arrays of id's to compare the string version of the arrays:

var groups = [{id: 1, name: "check 1"}, {id: 2, name: "check 2"}]

var checkedgroups = [{id: 1, name: "check 1"}, {id: 2, name: "check 2"}, {id: 3, name: "check 3"}]

function differenceBy(g, c, id){
  var id1 = JSON.stringify(g.map(i => i[id]));
  var id2 = JSON.stringify(c.map(i => i[id]));
  if(id1 == id2) return true;
  else return false;
}


console.log(differenceBy(groups, checkedgroups, 'id'))

score 0 · Answer 3 · answered Jan 24 '19 at 06:49

0

You can use isEqualWith as follows:

_.isEqualWith(array, other, (objValue, othValue) => {
  if(objValue.id === otherValue.id && objValue.name === otherValue.name){
   return true'
  }
})

answered Jan 24 '19 at 06:49

Umair Farooq

1,763
13
16

score 0 · Answer 4 · answered Jan 24 '19 at 06:50

0

If it's just a JSON string

try{
    return JSON.stringify(groups) === JSON.stringify(checkedgroups);
} catch(e) {
    return false
}

answered Jan 24 '19 at 06:50

hoythan

466
5
8

score 0 · Answer 5 · answered Jan 24 '19 at 06:53

If you want to get the number of items which differ from one array to another you can map both your objects to an array of id's (or whatever you set the prop argument to). You can then use .filter to get the difference of arr1 - arr2. Lastly, you can then return the .length of the difference between the two arrays.

See working example below:

const groups = [{id: 1, name: "check 1"}, {id: 2, name: "check 2"}],
checkedgroups = [{id: 1, name: "check 1"}, {id: 2, name: "check 2"}, {id: 3, name: "check 3"}];

const differenceBy = (arr1, arr2, prop) => {
  const arrProp1 = arr1.map((obj) => obj[prop]),
  arrProp2 = arr2.map((obj) => obj[prop]),
  
  dif = arrProp1.filter(num => !arrProp2.includes(num));
  return dif.length;
}

console.log(differenceBy(checkedgroups, groups, "id"));

score 0 · Answer 6 · answered Jan 24 '19 at 06:59

To compare any objects with each other (which have no circular reference) use these:

If you're sure whether they ain't null and undefined:
JSON.stringify(groups) === JSON.stringify(checkedgroups)

Otherwise:
JSON.stringify(groups || null) === JSON.stringify(checkedgroups || null)

How to check whether there is difference in two array in javascript?

6 Answers6