Convert Seconds to hours:minutes:seconds in JavaScript

function rectime(sec) 
{
var hr = Math.floor(sec / 3600);
var min = Math.floor((sec - (hr * 3600))/60);
sec -= ((hr * 3600) + (min * 60));
sec += ''; min += '';
while (min.length < 2) {min = '0' + min;}
while (sec.length < 2) {sec = '0' + sec;}
hr = (hr)?':'+hr:'';
return hr + min + ':' + sec;

}