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.

Answer 1

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.

Answer 2

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]) } } 

Answer 3

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!

Answer 4

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') } }) 

Answer 5

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)

Answer 6

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); 

Answer 7

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