Escaping 'script' Tags in String Literals

This section provides a tutorial example on how to use escape character in 'script' tags to prevent browser prematurely end embedded JavaScript code.

Now let's try to fix the problem we found in the previous section.

The first fix is to use the backslash character (\) to escape (/) in the </script> tag. This extra backslash will stop the browser to recognize this tag as the end of JavaScript code. At the same time, JavaScript engine will ignore this backslash and evaluate the string literal in the same way as without the extra backslash.

Here is the revised HTML document with the extra backslash character:

<!-- Escape_Script_Tag_Backslash.html
   Copyright (c) 2002 All Rights Reserved.
<head><title>Escaping Script Tags</title></head>
<script type="text/javascript">
   document.writeln("Question: How to use the <script> tag?");
   document.writeln("Answer: <script>...Script Code...<\/script>");
   document.writeln("Rate this answer: 1 | 2 | 3 | 4 | 5");

If you run this example script in a browser, you will get:

Question: How to use the 
Rate this answer: 1 | 2 | 3 | 4 | 5

Better? Yes. But this is still not what we expected. Here is what happened when the browser processes this HTML document:

In another word, there is no code error in the JavaScript code now. The execution of the JavaScript code inserted the following content into the "document" object:

Question: How to use the <script> tag:
Answer: <script>...Script Code...<\/script>
Rate this answer: 1 | 2 | 3 | 4 | 5

When the browser renders this content, it will treat "script" tags as HTML tags, causing some text not showing on the final page.

See the next section on how to protect "script" tags in HTML documents.

Table of Contents

 About This Book

 Introduction to JavaScript

 ECMAScript Language Specification and JavaScript Dialects

 Data Types, Variables and Expressions

 Flow Control Statements

 Creating, Accessing, and Manipulating Arrays

 Defining and Calling Functions

Web Browser Supporting JavaScript

 JavaScript Support in Web Browsers

 Including JavaScript Codes with HTML "script" Tags

 type="text/javascript" or language="JavaScript"

 JavaScript Version Supported by Browsers

 Including 'script' Tags in String Literals

Escaping 'script' Tags in String Literals

 Using HTML Entities to Protect HTML Tags

 Including JavaScript Codes as External Files

 DOM API - The "document" Object

 DOM API - The "window" Object

 DOM API - The "" Method

 Event Listeners and Objects

 'javascript:' Pseudo-URL Addresses

 JavaScript Console in Google Chrome

 JavaScript Console in Mozilla Firefox

 JavaScript Console in Apple Safari

 JavaScript Console in IE (Internet Explorer)

 Server-Side and Client-Side Web Scripting

 Introduction to Objects

 Defining Your Own Object Types

 Inheritance of Properties and Methods through the Prototype Object Chain

 'jrunscript' - JavaScript Shell Command from JDK

 Using Functions as "Function" Objects

 Introduction to Built-in Object Types

 W3C's Document Object Model (DOM) Specifications

 AJAX (Asynchronous JavaScript And XML)


 Full Version in PDF/EPUB