Javascript [Electronic resources] : The Definitive Guide (4th Edition) نسخه متنی

Availability

JavaScript 1.0; JScript 1.0, ECMAScript v1

Synopsis

string.indexOf(substring)
string.indexOf(substring,start)

Arguments

substring

The substring that is to be searched for within
string.

start

An optional integer argument that specifies the position within
string at which the search is to start.
Legal values are 0 (the position of the first character in the
string) to
string.length-1
(the position of the last character in the string). If this argument
is omitted, the search begins at the first character of the string.

Returns

The position of the first occurrence of
substring within
string that appears after the
start position, if any, or -1 if no
such occurrence is found.

Description

String.indexOf( ) searches the string
string from beginning to end to see if it
contains an occurrence of substring. The
search begins at position start within
string, or at the beginning of
string if start
is not specified. If an occurrence of
substring is found,
String.indexOf( ) returns the position of the
first character of the first occurrence of
substring within
string. Character positions within
string are numbered starting with zero.

If no occurrence of substring is found
within string, String.indexOf(
) returns -1.

Bugs

In JavaScript 1.0 and 1.1, if start is
greater than the length of string,
indexOf( ) returns the empty string, rather than
-1.

See Also

String.charAt( ), String.lastIndexOf( ), String.substring( )