JS indexof usage indexof () Definition and usage

IndexOf () Definition and usage

The IndexOf () method returns the position of the first occurrence of a specified string value in a string.

Grammar

Stringobject.indexof (Searchvalue,fromindex)

Parameters:

Searchvalue: Required. Specifies the string value that needs to be retrieved. An optional integer parameter.

Fromindex: Specifies where to start retrieving in the string. Its legal value is 0 to stringobject.length-1. If this argument is omitted, it is retrieved from the first character of the string.

Description

The method will retrieve the string stringobject from beginning to end to see if it contains substring searchvalue. The location at which to begin retrieving is at the fromindex of the string or at the beginning of the string (when no fromindex is specified). If a searchvalue is found, the position of the first occurrence of the Searchvalue is returned. The character position in Stringobject is starting at 0.

Hints and Notes

Note: the IndexOf () method is case-sensitive!

Note: If the string value that you want to retrieve does not appear, the method returns-1.

Instance

In this example, we will make a different search within the "Hello world!" string:

<script type= "Text/javascript" >    

var str= "Hello world!";  

document.write (Str.indexof ("Hello") + "<br/>");  

document.write (Str.indexof ("World"));    

</script>

The output of the above code:

0  -1  6   
Most uses:
Can be used to determine whether the mailbox is correct, such as

<script type= "Text/javascript" >    

if ((Yx.email.value.indexOf (' @ ', 0) ==-1) | | (Yx.email.value.indexOf ('. ', 0) ==-1))
{
Alter ("wrong email address");
Yx.email.focus ();
return false;
}
</script>

JS indexof usage indexof () Definition and usage