Web topic 21 pass info via javascript

Web Authoring

Topic 21 –
Passing Information via Javascript

Objectives
Students should able to:
1 Pass information via web forms using
the submit button.
2. Identify and use the various JavaScript
features:
• Variables.
• Custom and Build-in Functions
• alert()
• prompt()

What is Javascript?
JavaScript is a Web based programming
language. It can be used to create
dynamic Web pages.

A dynamic Web page changes its
appearance or the content depending on
the user input or the time.

Writing Javascript
A JavaScript program can be embedded
into our HTML code.

<HEAD>
<TITLE>My JavaScript page</TITLE>
<SCRIPT LANGUAGE= “text/JavaScript”>
</SCRIPT>
</HEAD>

Writing Javascript
Some points to note about when writing
Javascript.

All JavaScript commands should come in
between the <SCRIPT> and </SCRIPT>
tags

All JavaScript commands should be
followed by a semicolon (;)

Using Alert
ALERT commands are messages, which
pop up in a new small window.
They automatically get closed when the
user clicks OK button.

Syntax of the ALERT command:
<SCRIPT language = “text/JavaScript”>
alert(“Hello world!”);
</SCRIPT>

Using variable
We can use variables in JavaScript like
other programming languages
Use the var keyword to declare variables.
var secsPerMin = 60;

Variables must start with either a letter or
the underscore character.

Variable names are case-sensitive.

Using prompt command
The PROMPT command is used to get
information from the user.
Sample code:
var a = prompt(“What is your name?”);
var b = “Good Morning!” + a;
alert (b);

Using math operations
We can use MATH operations to do
calculations on the variables.
Sample code:
var secsPerHour = 0;
secsPerHour = 24 * 60 * 60;

alert (“The number of seconds in an year =” +
secsPerHour);

Displaying Text
If we want to display text on the Web
page, we can use the following
command:

document.write(“The number of
seconds in an year=” +secs_per_year);

Date object
<SCRIPT LANGUAGE=”JavaScript”>
var todayDate = new Date();
document.write("Today's Date is ")
document.write(todayDate.getDate());
document.write(todayDate.getMonth());
document.write(todayDate.getYear());
</SCRIPT>

Swapping Images
Using JavaScript you can change the
images when you place the mouse over
it.

This feature can be used to change
button images, decorate images and to
highlight the links.

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Web topic 21 pass info via javascript