CODEWITHSUNDEEP
javascriptarrayscompare
GNG
GNG

Reputation: 1531

Quickest way to check if 2 arrays contain same values in javascript

Is there a quicker or more efficient way to check that two arrays contain the same values in javascript?

Here is what I'm currently doing to check this. It works, but is lengthy.

    var arraysAreDifferent = false;
    for (var i = 0; i < array1.length; i++) {
      if (!array2.includes(array1[i])) {
        arraysAreDifferent = true;
      }
    }
    for (var i = 0; i < array2.length; i++) {
      if (!array1.includes(array2[i])) {
        arraysAreDifferent = true;
      }
    }

Upvotes: 4

Views: 1156

Answers (2)

Harsh Boricha
Harsh Boricha

Reputation: 133


function same(arr1, arr2){
    //----if you want to check by length as well 
    // if(arr1.length != arr2.length){
    //     return false;
    // }

    // creating an object with key => arr1 value and value => number of time that value repeat;
    let frequencyCounter1 = {};
    let frequencyCounter2 = {};
    for(let val of arr1){
        frequencyCounter1[val] = (frequencyCounter1[val] || 0) + 1;
    }
    for(let val of arr2){
        frequencyCounter2[val] = (frequencyCounter2[val] || 0) + 1;
    }
    for(let key in frequencyCounter1){
        //check if the key is present in arr2 or not 
        if(!(key in frequencyCounter2)) return false;
        //check the number of times the value repetiton is same or not;
        if(frequencyCounter2[key]!==frequencyCounter1[key]) return false;
    }
    return true;
}

Upvotes: 0

CertainPerformance
CertainPerformance

Reputation: 370679

To reduce computational complexity from O(n ^ 2) to O(n), use Sets instead - Set.has is O(1), but Array.includes is O(n).

Rather than a regular for loop's verbose manual iteration, use .every to check if every item in an array passes a test. Also check that both Set's sizes are the same - if that's done, then if one of the arrays is iterated over, there's no need to iterate over the other (other than for the construction of its Set):

const arr1Set = new Set(array1);
const arr2Set = new Set(array2);
const arraysAreDifferent = (
  arr1Set.size === arr2Set.size &&
  array1.every(item => arr2Set.has(item))

);

Upvotes: 5

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