Two-element data array, increment through values

var testData =
[
["mariopaleka","mp7777777"],
["nbavpaulz","lakers4"],
["chitownlegend","mj23chicago"],
["laurencetan8","loverboy"],
["dfalkson","77447744"],
];

var a = testData[$context.currentTrackIndex];

$prop.set("MessageClip", "user", a[0]);
$prop.set("MessageClip", "pass", a[1]);