JavaScript indexof Function Usage Description _ Basics

How to use: Strobj.indexof (str,startindex[optional])

Program code

Where Strobj is a required option. A String object or text.
STR is a must option. The substring to find in the string object.
startindex is optional. The integer value indicates where to start the lookup within a String object, starting at 0. If omitted, it is looked up from the beginning of the string.


Note: The indexof of JavaScript is case-sensitive.

The IndexOf function method in JavaScript returns an integer value that indicates the starting position of the substring of a string object. If no string is found, returns-1. If the startindex is a negative number, the startindex is treated as zero. If it is larger than the maximum character position index, it is considered to be the largest possible index.

The IndexOf function is to perform a lookup from left to right
The following example illustrates the use of the IndexOf function method.

Program code

var str1= "FDIEJDIFADF";
var str= "E";
var i=str1.indexof (str);
alert (i);



In front of said, IndexOf is the size of the write, sometimes this gives us a certain amount of trouble, then how to solve it? Of course, the easiest way to do this is to convert the characters to uppercase or lowercase with tolowercase or touppercase.
The code is as follows:

Program code

<script>
var Str = ' ABCDEF ';
var Str1 = ' BCD ';
Alert (Str.tolowercase (). IndexOf (Str1.tolowercase ()));
str2 = ' AbCdEf ';
Alert (Str2.tolowercase (). IndexOf (Str1.tolowercase ()));
</script>



The following method extends the indexof (from the network) using regular

Program code

<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 = "Absnegkiugfkalg";
Alert (Test.indexof ("Kiu", false));
</script>



The following extension is more powerful, it is compatible with the original IndexOf function, and can also be ignored size lookup (also from the network).

Program code

<script language= "JavaScript" >
String.prototype._indexof = String.prototype.indexOf;
String.prototype.indexOf = function ()
{
if (typeof (Arguments[arguments.length-1])!= ' Boolean ')
Return this._indexof.apply (this,arguments);
Else
{
var bi = arguments[arguments.length-1];
var thisobj = this;
var idx = 0;
if (typeof (Arguments[arguments.length-2]) = = ' number ')
{
IDX = arguments[arguments.length-2];
Thisobj = this.substr (idx);
}

var re = new RegExp (arguments[0],bi? ') I ': ');
var r = Thisobj.match (re);
return r==null?-1:r.index + idx;
}
}
Alert ("Bcssssasdfsdf". IndexOf (' A ', 3,true));
Alert ("Bcssssasdfsdf". IndexOf (' A ', 3));
</script>