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Need a function in javascript to swap 2 elements in an array

Answer 1

+7 A:

Your code is ridiculously long. If the array always contains two elements, why not do this?

function swap(arr) {
    return [arr[1], arr[0]];
}

Also, the correct way to call the function is:

arr = swap(arr);

If you want the function to modify its argument instead, do this instead:

function swap(ass) {
    var tmp = arr[1];
    arr[1] = arr[0];
    arr[0] = tmp;
}

...also, there's a built-in method called reverse on arrays:

arr.reverse();

Matti Virkkunen 2010-04-14 13:32:56

That helped a bit - now I need to work on the output, as it isn't giving me the array.Ta!

2010-04-14 13:52:34

From now on, please tag your homework questions a homework so I don't accidentally answer them.

Matti Virkkunen 2010-04-14 13:53:53

@Matti: I thought you had enough +1s until I read that comment lol.

Andy E 2010-04-14 13:56:02

Answer 2

A:

Slighty off topic, but this Array method swaps two elements of its array (general case) by the fastest possible way:

// swaps elements at index i and j in array this
// feature detection for destructuring assignment
Array.prototype.swap = (function () {
    var i=0, j=1;
    try { [i,j]=[j,i]; }
    catch (e) {}
    if(i) {
        return function(i,j) {
            [this[i],this[j]] = [this[j],this[i]];
            return this;
        }
    } else {
        return function(i,j) {
            var temp = this[i];
            this[i] = this[j];
            this[j] = temp;
            return this;
        }
    }
})();

Alsciende 2010-04-14 14:56:09

Answer 3

A:

    function swap(anArray) { 
        var length = anArray.length; 
        var returnArray = new Array(length); 
        for (var i = 0, j = length - 1; i < length; i++, j--) { 
            returnArray[j] = anArray[i]; 
        } 
        return returnArray;
    }

2010-04-14 15:13:07

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Need a function in javascript to swap 2 elements in an array

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