CODEWITHSUNDEEP
javascriptarrays
Kuan
Kuan

Reputation: 11389

Which is most efficient for a simple array iteration operation on array element

All:

Say I have an array of object, each one has value attr. What I want to do is :

Loop thru the array and remove the objects whose value is less than 1,

I thought of using splice or create another array, push those whose value>=1 into it then return new array, I wonder which way is better? Or any other efficient way?

Thanks

Upvotes: 0

Views: 78

Answers (4)

Sohail Arif
Sohail Arif

Reputation: 275

From the question if you are talking about array of object below is the solution which will keep intact the original array and its more efficient as well.

Use delete operator which will put undefined on indexes which have value<=1

<!doctype html>
<html>

<head>
  <script>
    var obj1 = {
      value: 0
    };
    var obj2 = {
      value: 10
    };

    var arr = [obj1, obj2];

    arr.forEach(function(x, counter, arr) {
      if (arr[counter].value <= 1)
        delete arr[counter];
    });
    arr.forEach(function(x, counter, arr) {
      document.write(arr[counter].value);
    });
  </script>
</head>

</html>

Upvotes: 0

cybersam
cybersam

Reputation: 66999

If you want to keep the original array intact:

arr.filter(function(elem) {
  return elem.value >= 1;
})

My reading of your question led me to understand that each array element has a value property. If, instead, each element is just the actual value being compared, then replace "elem.value" with "elem".

[UPDATE]

Based on a jsperf comparison, if you are OK with modifying the original array, the splice approach presented in @NicholasHazel's answer is actually an order of magnitude faster.

I even tried a third approach using slice() to first make a copy of the original array, and then using splice() on the copy, but that was much slower than the other approaches.

Upvotes: 2

Nicholas Hazel
Nicholas Hazel

Reputation: 3750

For efficiency sake, splice will be your most optimum performance solution. As long as you don't need the initial array any more, I would just convert the variable entirely.

var array = [-5,-4,-3,-2,-1,0,1,2,3,4,5];

for(var i=array.length-1; i>=0; i--){
    if(array[i] < 1) {
        array.splice(i,1);
    }
}

If you do have a need to utilize the initial array at a later time, pushing to a new array is your best bet:

var array = [-5,-4,-3,-2,-1,0,1,2,3,4,5];
var newArray = [];

for(var i=array.length-1; i>=0; i--){
    if(array[i] < 1) {
        newArray.push(array[i]);
    }
}

Both are perfectly reasonable solutions.

Upvotes: 1

metal03326
metal03326

Reputation: 1263

Internally splice is doing a new array, so behind the scenes you'll create new array for every object you want to remove. This means creating one array an pushing to it only wanted objects is much more efficient than splice.

Upvotes: 1

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