JavaScript substr() Method: String Object

Last update on August 19 2022 21:50:37 (UTC/GMT +8 hours)

Description

The substr() method returns the characters in a string starting at a specified position and continuing for a specified number of characters.

Version

Implemented in JavaScript 1.0

Syntax

substr(start_pos, length])

Parameter

start_pos: Specifies the position in the string where to begin extracting characters.

length: Specifies the number of characters to extract.

Note:

start_pos is a character index. The index of the first character is 0, and the index of the last character is 1 less than the length of the string.
If start_pos is positive and greater than the length of the string, substr() returns no characters.
If start_pos is negative, substr() uses it as a character index from the end of the string.
If length is 0 or negative, substr() returns no characters.
If the length is not defined , start extracts characters to the end of the string.

Example:

The following web document demonstrates how the substr() method can be used in various ways.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
<title>JavaScript String object - substr() method example</title>
</head>
<body>
<h1 style="color: red">JavaScript String object : substr() method</h1>
<hr />
<script type="text/javascript">
//This is done to make the following JavaScript code compatible to XHTML. <![CDATA[
var str = "abcdefghij"
document.write("Original string : "+str+"<br>")
document.write("(1,2) : ", str.substr(1,2)+"<br>")
document.write("(-2,2) : ", str.substr(-2,2)+"<br>")
document.write("(1) : ", str.substr(1)+"<br>")
document.write("(1,20) : ", str.substr(1,20)+"<br>")
document.write("(-20, 2) : ", str.substr(-20,2))
//]]>
</script>
</body>
</html>

View the example in the browser

Supported Browser

Internet Explorer 7	Firefox 3.6	Google Chrome 7	Safari 5.0.1	Opera 10
Yes	Yes	Yes	Yes	Yes

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