Bits & Bytes

Posts Tagged ‘validation’

Using an External JavaScript File

Putting JavaScript into a separate file has many advantages over writing the code inline in an HTML file. First, it makes the JavaScript code much cleaner since the HTML code is in a separate file. Second, it helps to promote modularization, which is always a benefit in programming. Finally, it the eliminates the need for creating CDATA sections to encapsulate JavaScript code that contains XHTML characters; we will explain this more later

Beginning with the code from our earlier JavaScript post, we have a simple HTML file, which I have called “JavaScriptBasis.html” in this post. The original HTML code with the embedded JavaScript code looks like this:

Old JavaScriptBasis.html

<!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=utf-8" />
  <title>XoaX.net</title>
</head>
<body>

<script type="text/javascript">
    document.write("Welcome to XoaX.net!");
</script>

</body>
</html>

What we want to do now is remove the JavaScript code, put it into a separate .js file, and call it via the script tag from the HTML file. To do this, use your favorite text editor to create a .js file called “BasicWrite.js” in the same directory as your HTML file and save it with this code pasted into it:

BasicWrite.js

document.write("Welcome to XoaX.net!");

Then open the file “JavaScriptBasis.html” and change code in the script tags to this:

<script type="text/javascript" src="BasicWrite.js"></script>

Now, your HTML file will call your JavaScript file. The code in the HTML file should look like this:

JavaScriptBasis.html

<!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=utf-8" />
  <title>XoaX.net</title>
</head>
<body>

<script type="text/javascript" src="BasicWrite.js"></script>

</body>
</html>

After you have saved the new files, double-click the HTML file to open it and you should see the message “Welcome to XoaX.net!” printed just as you did before.

It may not feel like much has been accomplished yet. In fact, it might seem like we have made the code more complex. However, the advantages will become more apparent when we write bigger programs.

Finally, we remark that using .js files allows us to eliminate the need to use CDATA sections. When XHMTL characters, like <, are used inside of an embedded JavaScript section, they create validation problems. For example, in order to allow this code to validate, we need the CDATA section as shown here:

CDATA Section


<script type="text/javascript">
var iX = 10;
/*<![CDATA[*/
if (iX < 13) {
    document.write("Welcome to XoaX.net!");
}
]]>
/*]]>*/
</script>

When this code is put into an external JavaScript, this CDATA section is not needed for validation. Note that the CDATA section looks particularly horrific since it requires us to comment out both endpoints of the CDATA section so that it does not adversely affect the JavaScript code:
. . .
/*<![CDATA[*/
. . .
/*]]>*/
. . .