JavaScript indexof Ignore case

IndexOf in JavaScript are strictly case-sensitive how do you ignore case? Put them all in uppercase or lowercase, then you can compare them. indexof The character position of the substring for the first time within the object with toLowerCase or toUpperCase (1)

< Script >
var ' ABCDEF ';
var ' BCD ';

Alert (Teststr.tolowercase (). IndexOf (Substr.tolowercase ()));
' AbCdEf ';
Alert (Teststr.tolowercase (). IndexOf (Substr.tolowercase ()));
</ Script >

(2)

<  script  >  String. prototype.  IndexOf = function  (f,m) {var  mm = (m = = false )?"
	 "I" : ; var  re = eval ( "/"  + F + "/" 
	+MM);
	var  rt = this . Match (re); return  (RT = = null )?	
-1:rt.index;

} var  test = ; Alert (Test.indexof (, false )); </ script  >