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

Availability

JavaScript 1.0; JScript 1.0, ECMAScript v1

Synopsis

string.lastIndexOf(substring)
string.lastIndexOf(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 where the search is to start. Legal
values are from 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 with the last character of the string.

Returns

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

Description

String.lastIndexOf( ) searches the string from end
to beginning to see if it contains an occurrence of
substring. The search begins at position
start within
string, or at the end of
string if start
is not specified. If an occurrence of
substring is found,
String.lastIndexOf( ) returns the position of the
first character of that occurrence. Since this method searches from
end to beginning of the string, the first occurrence found is the
last one in the string that occurs before the
start position.

If no occurrence of substring is found,
String.lastIndexOf( ) returns -1.

Note that although String.lastIndexOf( ) searches
string from end to beginning, it still
numbers character positions within string
from the beginning. The first character of the string has position 0
and the last has position
string.length-1.

See Also

String.charAt( ), String.indexOf( ), String.substring( )