Javascript swap array elements

If you want a single expression, using native javascript, remember that the return value from a splice operation contains the element(s) that was removed.

var A = [1, 2, 3, 4, 5, 6, 7, 8, 9], x= 0, y= 1;
A[x] = A.splice(y, 1, A[x])[0];
alert(A); // alerts "2,1,3,4,5,6,7,8,9"

Edit:

The [0] is necessary at the end of the expression as Array.splice() returns an array, and in this situation we require the single element in the returned array.

You only need one temporary variable.

var b = list[y];
list[y] = list[x];
list[x] = b;

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Edit hijacking top answer 10 years later with a lot of ES6 adoption under our belts:

Given the array arr = [1,2,3,4], you can swap values in one line now like so:

[arr[0], arr[1]] = [arr[1], arr[0]];

This would produce the array [2,1,3,4]. This is destructuring assignment.