JS: used to determine whether a string contains the indexOf () method, jsindexof

JS: used to determine whether a string contains the indexOf () method, jsindexof

Definition and usage

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

Syntax

stringObject.indexOf(searchvalue,fromindex)

Parameters	Description
Searchvalue	Required. Specifies the string value to be retrieved.
Fromindex	Optional integer parameter. Specifies the start position of the string. The valid value is 0 to stringObject. length-1. If this parameter is omitted, It is retrieved from the first character of the string.

Description

The indexOf method returns an integer. The character position in the stringObject starts from 0. If no substring is found,-1 is returned.

Example:

<Script type = "text/javascript"> var str = "Hello world! "; Alert (str. indexOf (" world "); // 6if (str. indexOf (" Hello ")! =-1) {alert ("included");} else {alert ("excluded") ;}</script>

Js checks whether a string contains a string

String. indexOf ("Check string")> 0 exists, <= 0 does not exist

Js determines whether a string is contained

If (a. indexOf ('], [') <0)
Does not contain
Else
Include