How to compare two array objects' particular string?

Question

I am little confused on how to compare two array objects' particular value get that neglected values as an array.

var Arr1 = [
 {
  jobId:"j1" 
 },
 {
  jobId:"j2" 
 },
 {
  jobId:"j3" 
 },
 {
  jobId:"j4" 
 },

]

var Arr2 = [
 {
  jobId:"j1" 
 },
 {
  jobId:"j2" 
 },

]

I want my result like this...

//neglected values

[
  {
  jobId:"j3" 
 },
 {
  jobId:"j4" 
 },
]

cheussy · Accepted Answer · 2016-12-23 18:25:23Z

3

So let's think about how to go about comparing things in two arrays.
It probably makes sense to assume in order to fully compare both arrays, we need to iterate them, making sure we compare every item in each array so that we can be sure
So if I was begining i would think of nesting for - loops. Why? Because it will iterate over the first array, on each index it hits the first array, it will then iterate over every element in the second array.
then you can create some basic if conditional logic like if Arr1[i] === Arr2[j], push one of the objects into an array.

answered Dec 23, 2016 at 18:25

cheussy

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2 Comments

RayfenWindspear Over a year ago

@torazaburo Has a better answer for advanced users, but this answer is better considering that the OP is just learning.

cheussy Over a year ago

@RayfenWindspear I agree, his answer is better, I purposely made it this way because he said he was beginning. I was just trying to outline a solution, because I remember when I started visualizing double for loops helped me understand things better. filtering it out, is a smarter approach for sure.

score 2 · Accepted Answer · 2016-12-23 18:31:41Z

Filter (Array#filter) down the elements of the first array to those for which there are not (!) some (Array#some) matching job IDs in the second array.

Arr1.filter(arr1Elt => !Arr2.some(arr2Elt => arr2Elt.jobId === arr1Elt.jobId))

Using line-by-line comment style:

Arr1                             // From Arr1,
  .filter(                       // keep
    arr1Elt =>                   // elements for which 
      !                          // it is not the case that
      Arr2                       // Arr2 has
        .some(                   // some
          arr2Elt =>             // elements for which 
            arr2Elt.jobId        // the job ID
            ===                  // is equal to
            arr1Elt.jobId        // the job ID from the first array.
        )
  )

Ori Drori · Accepted Answer · 2016-12-23 19:21:39Z

2

You can use lodash's _.differenceBy() to find the items from Arr1 missing from Arr2.

var Arr1 = [{"jobId":"j1"},{"jobId":"j2"},{"jobId":"j3"},{"jobId":"j4"}];
var Arr2 = [{"jobId":"j1"},{"jobId":"j2"}];

// find items that are in Arr1, but not in Arr2, compare items by their jobId
var result = _.differenceBy(Arr1, Arr2 , 'jobId');

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.3/lodash.min.js"></script>

edited Dec 23, 2016 at 19:21

answered Dec 23, 2016 at 18:54

Ori Drori

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Comments

kukkuz · Accepted Answer · 2016-12-23 18:29:16Z

1

You can use Array.prototype.filter on Arr1 and check if any of its entries are in Arr2 using Array.prototype.some - see demo below:

var Arr1=[{jobId:"j1"},{jobId:"j2"},{jobId:"j3"},{jobId:"j4"}];
var Arr2=[{jobId:"j1"},{jobId:"j2"}];

var result = Arr1.filter(function(e){
  return !Arr2.some(function(k){
    return k.jobId === e.jobId;
  });
});

console.log(result);

answered Dec 23, 2016 at 18:29

kukkuz

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