How to check if arrays have the same object React Native

Question

I have two arrays:

const array1 = [
    { id: 1, name: 'John', score: 124 },
    { id: 2, name: 'Angie', score: 80 },
    { id: 3, name: 'Max', score: 56 }
]

const array2 = [
    { id: 5, name: 'Lisa', score: 78  },
    { id: 2, name: 'Angie', score: 80 }
]

JSON.stringify(array1) == JSON.stringify(array2) is not a solution, because arrays have different number of objects.

array1.some(item=> array2.includes(item)) doesnt't work too.

If there a solution?

Diesel · Answer 1 · 2019-12-13T19:08:31.857

Here is a quick solution, maybe not the most performant.

  const array1 = [
    { id: 1, name: 'John', score: 124 },
    { id: 2, name: 'Angie', score: 80 },
    { id: 3, name: 'Max', score: 56 },
  ];

  const array2 = [
    { id: 5, name: 'Lisa', score: 78 },
    { id: 2, name: 'Angie', score: 80 },
  ];

  // Index will have -1 if there is no match, otherwise it'll have
  // the index of the first found match in array1.
  const index = array1.findIndex(array1Item => {

    // This will return the index if found, otherwise -1
    const match = array2.findIndex(array2Item => {
      // return array1Item.id === array2Item.id;
      return JSON.stringify(array1Item) === JSON.stringify(array2Item);
    });

    return match > -1;
  });

Instead of stringifying the entire object, if id is unique, you can just compare id as shown in the commented code.

Be advised this could have a complexity of O(n^2) where n is your array sizes. Big arrays may take a while.

Here is it running on PlayCode. It logs index as 1 because the first match is the second item in array1.

score 0 · Accepted Answer · answered Dec 14 '19 at 06:02

What i would suggest is since your id is unique , so try the below :

const array1 = [
    { id: 1, name: 'John', score: 124 },
    { id: 2, name: 'Angie', score: 80 },
    { id: 3, name: 'Max', score: 56 }
]

const array2 = [
    { id: 5, name: 'Lisa', score: 78  },
    { id: 2, name: 'Angie', score: 80 }
]


var array2Id = {}
array2.forEach(function(obj){
    bIds[obj.id] = obj;
});

// Return all elements in A, unless in B
let check =  array1.filter(function(obj){
    return !(obj.id in array2Id);
});

console.log(check,'there')

if check is an empty array that means both are same otherwise it will give the different objects.

Hope it helps feel free for doubts

How to check if arrays have the same object React Native

2 Answers2