Lodash finding difference between JSON arrays

Question

Using lodash for finding difference:

c1Arr is:

[ { varName: 'city', varValue: 'cccccccc' },
  { varName: 'country', varValue: 'dddddddd' }
 ]

c2Arr is:

[ { varName: 'abc', varValue: 'aaa' },
  { varName: 'city', varValue: 'cccccccc' },
  { varName: 'country', varValue: 'dddddddd' }
 ]

Executing the following code

    var dArr = _.difference(c2Arr, c1Arr);
    console.log(dArr);

Why don't I get the result :

[ { varName: 'abc', varValue: 'aaa' }]

Instead I get (i.e. c2Arr)

[ { varName: 'abc', varValue: 'aaa' },
  { varName: 'city', varValue: 'cccccccc' },
  { varName: 'country', varValue: 'dddddddd' }
 ]

Answer 1

You have to provide the comparator function, since the elements are object.

Try this,

_.differenceWith(c2Arr, c1Arr, _.isEqual);

var c1Arr = [{
  varName: 'city',
  varValue: 'cccccccc'
}, {
  varName: 'country',
  varValue: 'dddddddd'
}]

var c2Arr = [{
  varName: 'abc',
  varValue: 'aaa'
}, {
  varName: 'city',
  varValue: 'cccccccc'
}, {
  varName: 'country',
  varValue: 'dddddddd'
}]

var dArr = _.differenceWith(c2Arr, c1Arr, _.isEqual);
console.log(dArr);

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