How to compare 2 arrays of object with different length?

Question

I work on an angular application and I have to compare 2 arrays of object :

ar1 = [{id: 2, itemId: 1},
    {id: 5, itemId: 3},
    {id: 18,itemId: 13},
    {id: 16,itemId: 14}]

ar2 = [{id: 13, itemId: 1},
    {id: 12, itemId: 14}]

I try to do something like this:

for(let i = 0 ; i < this.ar1.length ; i++){
    if(this.ar2[i] != undefined){
        if(this.ar1[i].itemId == this.ar2[i].itemId){
            console.log("in and ==itemId",this.ar2[i])
        }
        else{
            console.log("in and !=itemId",this.ar1[i])
        }
    }
    else{
        console.log("undefined",this.ar1[i])
    }
}

It's return me that :

in and ==itemId {id: 13, itemId: 1}
in and !=itemId {id: 5, itemId: 3}
undefined {id: 18, itemId: 13}
undefined {id: 16, itemId: 14}

I want a function which can say me which object is in the 2 arrays and which object is not in the 2 arrays.

It's not a duplicate cause I don't want to see difference between 2 arrays of object but see if the itemId if the same and get the object with the same itemId.

Possible duplicate of [How to get the difference between two arrays of objects in JavaScript](https://stackoverflow.com/questions/21987909/how-to-get-the-difference-between-two-arrays-of-objects-in-javascript) — Shibon, Mar 12 '19 at 10:08
I have create a stackblitz to solve your problem https://stackblitz.com/edit/angular-gmhktk?file=src%2Fapp%2Fapp.component.ts — TheParam, Mar 12 '19 at 10:15

score 2 · Answer 1 · answered Mar 12 '19 at 10:15

You want to iterate over both arrays so you can compare all of the values of ar1 with all of the values of ar2.

Here is the basic logic to run the code snippet:

let ar1 = [
  {id: 2, itemId: 1},
  {id: 5, itemId: 3},
  {id: 18,itemId: 13},
  {id: 16,itemId: 14}
];

let ar2 = [
  {id: 13, itemId: 1},
  {id: 12, itemId: 14}
];

for (let x = 0; x < ar1.length; x++) {
  for (let y = 0; y < ar2.length; y++) {
    if (ar1[x].itemId === ar2[y].itemId) {
      console.log("id: " + ar1[x].id + ", itemId: " + ar1[x].itemId + " = id: " + ar2[y].id + ", itemId: " + ar2[y].itemId);
    }
  }
}

You can simplify this further by using forEach instead of traditional for loops. You can also change the console.log logic to fit whatever data you are expecting to output.

score 2 · Accepted Answer · answered Mar 12 '19 at 10:20

You have t iterate over both array and find it id of arr1 is present in arr2 or not

ar1 = [{
    id: 2,
    itemId: 1
  },
  {
    id: 5,
    itemId: 3
  },
  {
    id: 18,
    itemId: 13
  },
  {
    id: 16,
    itemId: 14
  }
]

ar2 = [{
    id: 13,
    itemId: 1
  },
  {
    id: 12,
    itemId: 14
  }
]

for (let i = 0; i < this.ar1.length; i++) {
  id = false;
  for (let j = 0; j < this.ar2.length; j++) {
    if (this.ar1[i].itemId == this.ar2[j].itemId) {
      id = true
      data = this.ar2[j];
    }

  }
  if (id) {
    console.log("in and ==itemId", data)
  } else {
    console.log("in and !=itemId", this.ar1[i])
  }
}

Sharan Arumugam · Answer 3 · 2019-03-12T11:37:57.017

1

How about .includes()?

ar1 = [
  {id: 2, itemId: 1},
  {id: 5, itemId: 3},
  {id: 18, itemId: 13},
  {id: 16, itemId: 14},
];

ar2 = [
  {id: 2, itemId: 1},
  {id: 5, itemId: 25},
  {id: 18, itemId: 13},
  {id: 22, itemId: 14},
];

intersection = ar1.filter(x => ar2.map(y => y.itemId).includes(x.itemId));
console.log(intersection);

Peace

edited Mar 12 '19 at 11:37

answered Mar 12 '19 at 11:33

Sharan Arumugam

353
6
12

score 0 · Answer 4 · answered Mar 12 '19 at 10:10

Instead of using traditional for use foreach which will traverse every element from the array and check with another element in the array.

your.component.ts

export class AppComponent {
  name = 'Angular';

  ar1 = [{ id: 2, itemId: 1 },
  { id: 5, itemId: 3 },
  { id: 18, itemId: 13 },
  { id: 16, itemId: 14 }]

  ar2 = [{ id: 13, itemId: 1 },
  { id: 12, itemId: 14 }]

 constructor () {
   this.compareArray()
 }


  compareArray() {

    this.ar1.forEach( array1Ttem => {

      this.ar2.forEach( array2Item => {

         if(array1Ttem.itemId == array2Item.itemId){
            console.log("in and ==itemId",array1Ttem);
        }
        else{
            console.log("in and !=itemId",array1Ttem);
        }

      })
    })
  }
}

Solution on Stackblitz

Hope this will help!

score 0 · Answer 5 · answered Mar 12 '19 at 10:12

You can iterate ar1 and use findIndex to check if there exist an object on ar2 which has same itemId

let ar1 = [{
    id: 2,
    itemId: 1
  },
  {
    id: 5,
    itemId: 3
  },
  {
    id: 18,
    itemId: 13
  },
  {
    id: 16,
    itemId: 14
  }
]

let ar2 = [{
    id: 13,
    itemId: 1
  },
  {
    id: 12,
    itemId: 14
  }
]

ar1.forEach(function(item) {

  let findIndexInar2 = ar2.findIndex(function(elem) {
    return item.itemId === elem.itemId;
  })

  if (findIndexInar2 !== -1) {
    console.log('itemId present in ar2')

  } else {
    console.log('itemId not present in ar2')

  }



})

score -1 · Answer 6 · answered Mar 12 '19 at 10:13

Just like this :

const ar1 = [
  { id: 2, itemId: 1 },
  { id: 5, itemId: 3 },
  { id: 18, itemId: 13 },
  { id: 16, itemId: 14 },
]

const ar2 = [{ id: 13, itemId: 1 }, { id: 12, itemId: 14 }]
const inTwoArray = []
const notInTwoArray = []
ar1.forEach(el => {
  if (ar2.find(el1 => el1.itemId === el.itemId)) {
    inTwoArray.push(el)
  } else {
    notInTwoArray.push(el)
  }
})

console.log(inTwoArray)
console.log(notInTwoArray)

Tushar Walzade · Answer 7 · 2019-03-12T11:41:49.763

The following snippet will help you to find where your itemId is common -

let ar1 = [{ id: 2, itemId: 1 },
    { id: 5, itemId: 3 },
    { id: 18, itemId: 13 },
    { id: 16, itemId: 14 }
];

let ar2 = [{ id: 13, itemId: 1 },
    { id: 12, itemId: 14 }
];

let checkCommonElements = function(arr1, arr2) {
    arr1.forEach((object1, index1) => {
     let flag = false;
        arr2.forEach((object2, index2) => {
            if (object1.itemId === object2.itemId) {
             flag = true;
                console.log("Item present in ar2: ", JSON.stringify(object1));
            }
        });
        if(!flag) {
            console.log("Item not in ar2: ", JSON.stringify(object1));
        }
    });
}

checkCommonElements(ar1, ar2);

How to compare 2 arrays of object with different length?

7 Answers7