[B@rmaley.e><e]

String.prototype.hasAt = function(needle, pos)
{
	var i = Math.min(this.length, Math.max(0, Number(pos) || 0));
	var j;
	var found;
	for ( ; i < this.length; i++) {
		if ( found ) {
			if ( i - j == needle.length ) {
				return j;
			}
			found = this.charAt(i) == needle.charAt(i - j);
		} else {
			found = this.charAt(i) == needle.charAt(0);
			if ( found ) {
				j = i;
			}
		}
	}
	return found && this.length - j == needle.length 
		? j 
		: -1;
};

var s1 = 'aababababaO_o',   
    l1 = 'ababaO';   
alert( [
  [s1.hasAt(l1), s1.indexOf(l1)] 
].join('\n') );

Кто еще верит, что все так просто?