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

Availability

JavaScript 1.0; JScript 1.0, ECMAScript v1

Synopsis

string.substring(from, to)

Arguments

from

An integer that specifies the position within
string of the first character of the
desired substring.

to

An optional integer that is one greater than the position of the last
character of the desired substring. If this argument is omitted, the
returned substring runs to the end of the string.

Returns

A new string, of length to-from, which contains a
substring of string. The new string
contains characters copied from positions
from to to -1
of string.

Description

String.substring( ) returns a substring of
string consisting of the characters
between positions from and
to. The character at position
from is included, but the character at
position to is not included.

If from equals
to, this method returns an empty (length
0) string. If from is greater than
to, this method first swaps the two
arguments and then returns the substring between them.

It is important to remember that the character at position
from is included in the substring but that
the character at position to is not
included in the substring. While this may seem arbitrary or
counterintuitive, a notable feature of this system is that the length
of the returned substring is always equal to
to -from.

Note that String.slice( ) and the nonstandard
String.substr( ) can also be used to extract
substrings from a string.

Bugs

In Netscape's implementations of JavaScript, when language
Version 1.2 is explicitly requested (with the
language attribute of a
<script> tag, for example), this method does
not correctly swap its arguments if from
is greater than to. Instead it returns the
empty string.

See Also

String.charAt( ), String.indexOf( ), String.lastIndexOf( ),
String.slice( ), String.substr( )