JavaScript substr() Method: String Object


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


Implemented in JavaScript 1.0


substr(start_pos, length])


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

length: Specifies the number of characters to extract.


  • 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.


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"
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
<title>JavaScript String object - substr() method example</title>
<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))

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

See also:

JavaScript Core objects, methods, properties.

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