Thursday, 3 July 2014

Chapter 5: Where To / How To

Like most programming languages the default behaviour when JavaScript when runs is to start at the first statement and move down executed each of them one by one. This will happened when the browser sees your code. We can put the script tag in <head> section, in <body> section in our html page or in the middle. The best practise for most of the web designers is to add the script tag just before the closing body tag.
Example:
<html>
<head>
<title>Untitled Document</title>
</head>
<body>
<div id="demo">
<h1>This is a heading.</h1>
<p>This is a paragraph.</p>
</div>
<script>
alert("This is a simple alert.");
</script>
</body>
</html>


Now when we execute the above code in browser the code will be executed line by line through the HTML and when sees the script tag it will be executed after the HTML content, and that what we want.

But if you add the script tag inside the head section the code will first alert the JavaScript and then will execute our html, and we don’t want that:
Example:
<html>
<head>
<title>Untitled Document</title>
<script>
alert("This is a simple alert.");
</script>
</head>
<body>
<div id="demo">
<h1>This is a heading.</h1>
<p>This is a paragraph.</p>
</div>
</body>
</html>
                  
                  
The next question is where to put JavaScript. Well, it’s not god practice to mix JavaScript with html because it will be hard to edit and read. That’s because of this we use separate JavaScript file in which you done need to add the script tag. Just type your JavaScript.
Here is an example how to add external JavaScript file which have to be in the body section again.
Inside the src=““attribute add the path location of your script which must be with .js extension.
                            
Example:
<html>
<head>
<title>Untitled Document</title>
</head>
<body>
<div id="demo">
<h1>This is a heading.</h1>
<p>This is a paragraph.</p>
</div>
<script src="script.js"></script>
</body>
</html>



We suggest you to put stylesheets and the top, the scripts at the bottom.