Javascript-Intro

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Transcript Javascript-Intro 

Javascript

JavaScript is what is called a client-side
scripting language:


a programming language that runs inside an
Internet browser (a browser is also known as a Web
client because it connects to a Web server to
download pages)
Inside a normal Web page you place some
JavaScript code. When the browser loads the
page, the browser has a built-in interpreter that
reads the JavaScript code it finds in the page
and runs it.
Possible Usage

Web page designers use JavaScript in many
different ways:

One of the most common is to do field validation in
a form. Many Web sites gather information from
users in online forms, and JavaScript can help
validate entries. For example, the programmer
might validate that a person's age entered into a
form falls between 1 and 120.

Another way that web page designers use
JavaScript is to create calculators.
Simple Calculator (1)

The HTML below shows you how to create a
Fahrenheit to Celsius converter using
JavaScript:
<HEAD>
<SCRIPT>
function temp(form)
{
var f = parseFloat(form.DegF.value, 10);
var c = 0;
c = (f - 32.0) * 5.0 / 9.0;
form.DegC.value = c;
}
</SCRIPT>
</HEAD>
Simple Calculator (2)

In the body of the page there is a typical form:
<FORM>
<h2>Fahrenheit to Celsius Converter</h2>
Enter a temperature in degrees F:
<INPUT NAME="DegF" VALUE="0" MAXLENGTH="15" SIZE=15>
<p>
Click this button to calculate the temperature in degrees C:
<INPUT NAME="calc" VALUE="Calculate" TYPE=BUTTON
onClick=temp(this.form)>
<p>
Temperature in degrees C is:
<INPUT NAME="DegC" READONLY SIZE=15>
</FORM>