CODEWITHSUNDEEP
javascriptarraysfor-loopnested-for-loop
Henry
Henry

Reputation: 259

Compare two arrays of objects using nested for loop

I have two arrays of objects that I'm going to compare. If the values in all properties are the same then I want to remove the property in arr1. Below is the arrays with objects. They have the same values but just in a different order. The problem is when I console.log arr1 I always have { foo: '', bar: '594' } left in the array.

const arr1 = [
  { foo: '061', bar: '591' },
  { foo: '061', bar: '592' },
  { foo: '070', bar: '593' },
  { foo: '', bar: '594' }
]

const arr2 = [
  { foo: '061', bar: '591' },
  { foo: '061', bar: '592' },
  { foo: '', bar: '594' },
  { foo: '070', bar: '593' }
]

Below is my nested for loop

for (let i = 0; i < arr1.length; i++) {
      for (let j = 0; j < arr2.length; j++) {
        if (arr1[i].foo === arr2[j].foo
          && arr1[i].bar === arr2[j].bar) {
          arr1.splice(i, 1)
        }
      }
    }

Upvotes: 0

Views: 555

Answers (1)

AngYC
AngYC

Reputation: 3933

The reason is because whenever you perform a splice function, the array size has been modified, thus the arr1.length will change in each of the iteration of i. In order to solve this, you can consider modifying the i value directly in your loop to restart the comparison.

const arr1 = [
  { foo: '061', bar: '591' },
  { foo: '061', bar: '592' },
  { foo: '070', bar: '593' },
  { foo: '', bar: '594' }
];

const arr2 = [
  { foo: '061', bar: '591' },
  { foo: '061', bar: '592' },
  { foo: '', bar: '594' },
  { foo: '070', bar: '593' }
];

for (let i = 0; i < arr1.length; i++) {
  for (let j = 0; j < arr2.length; j++) {
    if (arr1[i].foo === arr2[j].foo && arr1[i].bar === arr2[j].bar) {
      arr1.splice(i, 1);
      // Restart the current i in next iteration
      i--;
      break;
    }
  }
}

console.log(arr1);

Upvotes: 1

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