indexOf() not working

1

I have a search field that is searching an array:


for (i=0; i< searchStrings_ar.length; i++) {
	index = searchStrings_ar*.toLowerCase().indexOf(searchCriteria);
	 if( index > -1 ) {
		searchResults_ar.push(i+1);
	}
}

Their is a data in the searchStrings array, I know that. If I trace out index, I get all of them undefined???

searchCriteria is just a variable of searchfield.text;

so nothing passed is getting undefined until I try and trace out index. Anyone have an idea?