Revision 339083 of String.prototype.lastIndexOf()

  • Revision slug: JavaScript/Reference/Global_Objects/String/lastIndexOf
  • Revision title: String.lastIndexOf
  • Revision id: 339083
  • Created:
  • Creator: ethertank
  • Is current revision? No
  • Comment CleanUp.

Revision Content

Summary

Returns the index within the calling String object of the last occurrence of the specified value, or -1 if not found. The calling string is searched backward, starting at fromIndex.

Method of String
Implemented in JavaScript 1.0
ECMAScript Edition ECMAScript 1st Edition

Syntax

string.lastIndexOf(searchValue[, fromIndex])

Parameters

searchValue
A string representing the value to search for.
fromIndex
The location within the calling string to start the search from, indexed from left to right. It can be any integer between 0 and the length of the string. The default value is the length of the string.

Description

Characters in a string are indexed from left to right. The index of the first character is 0, and the index of the last character is stringName.length - 1.

"canal".lastIndexOf("a")   // returns 3
"canal".lastIndexOf("a",2) // returns 1
"canal".lastIndexOf("a",0) // returns -1
"canal".lastIndexOf("x")   // returns -1

The lastIndexOf method is case sensitive. For example, the following expression returns -1:

"Blue Whale, Killer Whale".lastIndexOf("blue"); // returns -1

Examples

Example: Using indexOf and lastIndexOf

The following example uses indexOf and lastIndexOf to locate values in the string "Brave new world".

var anyString = "Brave new world";

// Displays 8
document.write("<P>The index of the first w from the beginning is " +
   anyString.indexOf("w"));

// Displays 10
document.write("<P>The index of the first w from the end is " +
   anyString.lastIndexOf("w"));

// Displays 6
document.write("<P>The index of 'new' from the beginning is " +
   anyString.indexOf("new"));

// Displays 6
document.write("<P>The index of 'new' from the end is " +
   anyString.lastIndexOf("new"));

See also

Revision Source

<h2 id="Summary" name="Summary">Summary</h2>

<p>Returns the index within the calling <code>String</code> object of the last occurrence of the specified value, or -1 if not found. The calling string is searched backward, starting at <code>fromIndex</code>.</p>

<table class="standard-table">
  <thead>
    <tr>
      <th class="header" colspan="2">Method of <a href="/en-US/docs/JavaScript/Reference/Global_Objects/String" title="JavaScript/Reference/Global_Objects/String"><code>String</code></a></th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>Implemented in</td>
      <td>JavaScript 1.0</td>
    </tr>
    <tr>
      <td>ECMAScript Edition</td>
      <td>ECMAScript 1st Edition</td>
    </tr>
  </tbody>
</table>


<h2 id="Syntax" name="Syntax">Syntax</h2>
<pre class="syntaxbox"><code><em>string</em>.lastIndexOf(<em>searchValue</em>[, <em>fromIndex</em>])</code></pre>


<h3 id="Parameters" name="Parameters">Parameters</h3>
<dl>
  <dt><code>searchValue</code></dt>
  <dd>A string representing the value to search for.</dd>
  <dt><code>fromIndex</code></dt>
  <dd>The location within the calling string to start the search from, indexed from left to right. It can be any integer between 0 and the length of the string. The default value is the length of the string.</dd>
</dl>

<h2 id="Description" name="Description">Description</h2>

<p>Characters in a string are indexed from left to right. The index of the first character is 0, and the index of the last character is <code>stringName.length - 1</code>.</p>

<pre class="brush: js">
"canal".lastIndexOf("a")   // returns 3
"canal".lastIndexOf("a",2) // returns 1
"canal".lastIndexOf("a",0) // returns -1
"canal".lastIndexOf("x")   // returns -1
</pre>

<p>The <code>lastIndexOf</code> method is case sensitive. For example, the following expression returns -1:</p>

<pre class="brush:js">"Blue Whale, Killer Whale".lastIndexOf("blue"); // returns -1</pre>


<h2 id="Examples" name="Examples">Examples</h2>


<h3 id="Example:_Using_indexOf_and_lastIndexOf" name="Example:_Using_indexOf_and_lastIndexOf">Example: Using <code>indexOf</code> and <code>lastIndexOf</code></h3>
<p>The following example uses <code>indexOf</code> and <code>lastIndexOf</code> to locate values in the string "<code>Brave new world</code>".</p>


<pre class="brush:js">
var anyString = "Brave new world";

// Displays 8
document.write("&lt;P&gt;The index of the first w from the beginning is " +
   anyString.indexOf("w"));

// Displays 10
document.write("&lt;P&gt;The index of the first w from the end is " +
   anyString.lastIndexOf("w"));

// Displays 6
document.write("&lt;P&gt;The index of 'new' from the beginning is " +
   anyString.indexOf("new"));

// Displays 6
document.write("&lt;P&gt;The index of 'new' from the end is " +
   anyString.lastIndexOf("new"));
</pre>


<h2 id="See_also" name="See_also">See also</h2>
<ul><li><a href="/en-US/docs/JavaScript/Reference/Global_Objects/String/charAt" title="JavaScript/Reference/Global_Objects/String/charAt">charAt</a>, <a href="/en-US/docs/JavaScript/Reference/Global_Objects/String/indexOf" title="JavaScript/Reference/Global_Objects/String/indexOf">indexOf</a>, <a href="/en-US/docs/JavaScript/Reference/Global_Objects/String/split" title="JavaScript/Reference/Global_Objects/String/split">split</a></li>
</ul>

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