How to compare two arrays of objects to find the differences

Question

Actually, I meet with an iterate problem when I compare two arrays of objects.

Array Old:

[{uuid:'a'}, {uuid:'b'}, {uuid:'c'}]

Array New:

[{uuid:'a'}, {uuid:'e'}, {uuid:'f'}]

what I am going to do is calling the api under the below logic:

compare 'new' with 'old' to get the result:

[{name:1, uuid:'e'}, {name:1, uuid:'f'}]

and then call the POST api one by one to add new uuid: 'e' and 'f'

compare 'new' with 'old' to get the result:

[{name:1, uuid:'b'},{name:1, uuid:'c'}]

and then call the Delete api one by one to delete uuid: 'b' and 'c'

I have tried the below code to find the difference, but it seems not correct:(need some help)

  const postArr = [];
  for (var i = 0; i < this.new.length; i++) {
    for (var o = 0; o < this.old.length; o++) {
      if (
        this.new[i].uuid !==
        this.old[o].uuid
      ) {
        postArr.push(this.new[i]);
      }
    }
  }
  console.log(postArr);

You should use the array filter method to achieve this.

Rajat Verma
– Rajat Verma

2020-04-19 08:54:14 +00:00
Commented Apr 19, 2020 at 8:54 — Rajat Verma
– Rajat Verma, Commented Apr 19, 2020 at 8:54

Cagri Tacyildiz · Accepted Answer · 2020-04-19 09:19:42Z

2

with filter and mapping u can achive uniques in old array

var a=[{uuid:'a'}, {uuid:'b'}, {uuid:'c'}];
 var b=[{uuid:'a'}, {uuid:'e'}, {uuid:'f'}];
 var keys = ['uuid'];
 
 console.log(findDifferences(a,b))



function findDifferences(objectA, objectB) {
 
  var result = objectA.filter(function(o1){
    return !objectB.some(function(o2){
        return o1.uuid === o2.uuid;       
    });
  }).map(function(o){

      return keys.reduce(function(newo, name){
          newo[name] = o[name];
          return newo;
      }, {});
  });
  return result;
}

edited Apr 19, 2020 at 9:19

answered Apr 19, 2020 at 8:51

Cagri Tacyildiz

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Comments

Vipin · Accepted Answer · 2020-04-19 09:55:41Z

Try this instead:

    function difference(checkingArray, baseArray) {
        let diff = [];
        let found = 0;
        for (let j = 0; j<checkingArray.length; j++) {
            found = 0;
            for (let i = 0; i<baseArray.length; i++) {
                if (baseArray[i].uuid == checkingArray[j].uuid) {
                    found = 1;
                    break;
                }
            }
            if (found == 0) {
                for (let k = 0; k<diff.length; k++) {
                    if (diff[k].uuid == checkingArray[j].uuid) {
                        found = 1;
                        break;
                    }
                }
                if (found == 0) {
                    diff.push(checkingArray[j]);
                }
            }
        }
        return diff;
    }


    let old = [{uuid:'a'}, {uuid:'b'}, {uuid:'c'}];

    let recent = [{uuid:'a'}, {uuid:'e'}, {uuid:'f'}];

    let onlyOnNewArray = difference(recent, old); // returns elements only in recent array not in old array
    let onlyOnOldArray = difference(old, recent); // returns elements only in old array not in recent array

    console.log("only on old array", onlyOnOldArray);
    console.log("only on recent array", onlyOnNewArray);

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