var a = [];
var b = [];
var three = [1, 2, 3];
extend(a, three, 1);
alert( objEqual(a, [2, 3]), "extend to an empty array" );
extend(a, three, 1)
alert( objEqual(a, [2, 3, 2, 3]), "extend to a non-empty array" );
extend(b, three);
alert( objEqual(b, three), "extend of an empty array" );
var c1 = extend(null, three);
alert( objEqual(c1, three), "extend null" );
var c2 = extend(undefined, three);
alert( objEqual(c2, three), "extend undefined" );