php strpos - javascript equivalent

http://phpjs.org/functions/strpos/

function strpos (haystack, needle, offset) {
// http://kevin.vanzonneveld.net
// + original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
// + improved by: Onno Marsman // + bugfixed by: Daniel Esteban
// + improved by: Brett Zamir (http://brett-zamir.me)
// * example 1: strpos('Kevin van Zonneveld', 'e', 5);
// * returns 1: 14

var i = (haystack + '').indexOf(needle, (offset || 0)); return i === -1 ? false : i; }

strpos('Kevin van Zonneveld', 'e', 5); // return 1,14