How to duplicate elements in a js array?

Question

Whats the easiest way (with \"native\" javascript) to duplicate every element in a javascript array?

The order matters.

For example:

Answer 1

Just splice a little bit.

var a = [2, 3, 1, 4],
    i = a.length;
while (i--) {
    a.splice(i, 0, a[i]);
}
document.write('
' + JSON.stringify(a, 0, 4) + '
');