Lecture6

Basics JavaScript
By Sazilah Salam

Learning Outcome
At the end of this lesson, students should be
able to:
i) Insert JavaScripts in HTML documents
ii) Declare JavaScript variables in HTML
documents

JavaScript Syntax
• The HTML <script> tag is used to insert a JavaScript into an
HTML page.

The <script> tags tell
the browser to expect
a script in between
them.

<html>
<body>
<script type="text/javascript">
document.write("JavaScript is not Java");
</script>
</body>
This part that
</html>

writes/display the
actual text
3

Where to put your scripts?
1.
2.
3.
4.

Scripts in <head>
Scripts in <body>
In both the body and the head section
Using an External JavaScript

4

Where to put your scripts? <head>.
<html>
<head>
function message()
{
alert("This alert box was called with the onload event");
}
</script>
</head>

<body onload="message()">
</body>
</html>
5

Where to put your scripts? <body>.
<html>
<body>
document.write("JavaScript is not Java");
</script>
</body>
</html>
6

Where to put your scripts? <head> and <body>
• <html>
<head>
function message()
{
alert("This alert box was called with the onload event");
}
</script>
</head>
<body onload="message()">
document.write("This message is written by JavaScript");
</script>
</body>
</html>

7

Where to put your scripts? External javascript
• <html>
<head>
<script type="text/javascript" src="xxx.js"></script>
</head>
<body>
JavaScript external
</body>
file with a .js file
</html>
extension.

8

9

JAVASCRIPT VARIABLES
Rules for variable names:
• Variable names are case sensitive
• They must begin with a letter or the underscore character
• You can create a variable with the var statement:
var strname = some value

• You can also create a variable without the var statement:
strname = some value
•

Assign a Value to a Variable
var strname = "Hege"
Or like this:

strname = "Hege"

<html>
<body>
var firstname;
firstname=“Toot";
document.write(firstname);
document.write("<br />");
firstname=“Tweet";
document.write(firstname);
</script>

javascript variables
firstname=“Toot";

variable

value

<p>The script above declares a variable, assigns a value to it, displays
the value, changes the value, and displays the value again.</p>
</body>
</html>

Lecture6

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