Question

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Javascript swap array elements

I have a array like this:

this.myArray = [0,1,2,3,4,5,6,7,8,9];

Now what I want to do is, swap positions of two items give their positions.
For example, i want to swap item 4 (which is 3) with item 8 (which is 7)
Which should result in:

this.myArray = [0,1,2,7,4,5,6,3,8,9];

How can I achieve this?

Answer 1

Just reassign the elements, creating an intermediate variable to save the first one you over-write:

var swapArrayElements = function(arr, indexA, indexB) {
  var temp = arr[indexA];
  arr[indexA] = arr[indexB];
  arr[indexB] = temp;
};
// You would use this like: swapArrayElements(myArray, 3, 7);

If you want to make this easier to use, you can even add this to the builtin Array prototype (as kennebec@ suggests); however, be aware that this is generally a bad pattern to avoid (since this can create issues when multiple different libraries have different ideas of what belongs in the builtin types):

Array.prototype.swap = function(indexA, indexB) {
   swapArrayElements(this, indexA, indexB);
};
// You would use this like myArray.swap(3, 7);

Note that this solution is significantly more efficient than the alternative using splice(). (O(1) vs O(n)).