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Introduction and a First Script

 
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Introduction


This course deals with Scripts. A Script is a segment of code that manipulates the browser and its contents in ways that is not possible with ordinary HTML or Cascading Style Sheets. By using a script in your web pages, you can gain more control of how the page looks and behaves: dates and times can be added to the page, form elements validated before the contents are sent, browser details checked, cookies set, even simple games can be added to a web page - all with a scripting language.

The learning curve for scripting is a lot a steeper than HTML and Style Sheets. But you can learn the basics, and use scripts on your own pages, without it causing you too much trouble. The scripting language covered in these pages is meant to get you started on the subject, and is not intended as an in-depth study.

We're going to study the JavaScript programming language, because it is a widely-used scripting language for web pages. All the scripts in these pages have been tested with modern versions of a wide variety of browsers. If you're ready, then, let's make a start.

 

A First Script


Let's jump right in with a bit of code. Fire up whatever HTML Editor you use (you can use our free Editor by clicking here: Download the free editor ). With your editor open, copy the following code. When you're done copying it, save your work and load it into your browser.

<HTML>
<HEAD>
<TITLE>A First Script</TITLE>
</HEAD>
<BODY>

<SCRIPT LANGUAGE = JavaScript>

document.write("Hello World")

</SCRIPT>

</BODY>
</HTML>


All right, how did you get on? All that typing should have gotten you this in the browser:

"Hello World"

Granted, that's a heck of a lot of trouble to go to just to write "Hello World". But it's a start. Let's explain what's going on.

When you're writing your scripts, you enclose them between two <SCRIPT> tags, an opening one and a closing one. The opening one should tell the browser what language the script is written in:

<SCRIPT LANGUAGE = JavaScript>

The closing Script tag is just the word SCRIPT in between two angle brackets with a forward slash:

</SCRIPT>

Most of your JavaScript will go between these two tags. So what's all that "document dot write" bit?

document.write("Hello World")


Document is part of something called the Document Object Model. Document refers to all the text and HTML elements between the two BODY tags. And that includes any attributes inside the BODY tag itself. Like BGCOLOR.

Write( ) is a method of Document. A method is a bit of code that actually does something. As opposed to a Property, which IS something. Methods are usually Verbs, and Properties usually Nouns. The Write( ) method writes text (and numbers as well) between the two BODY tags on your page.

For all you English language experts out there who might be protesting about the lack of capital letters, Document is spelt with a lowercase "d", and Write with a lowercase "w". Try changing your code to this and see what happens:

Document.Write("Hello World")

JavaScript is damned picky about capital letters - it doesn't like them at all!

The part or parts between the two brackets of write( ) are what will be written to your page. Direct text goes between two double quotes; Variables don't need any. Whoops, we haven't done variables yet. We'll get to them.

So the whole line reads "Write the text Hello World between the two BODY tags of the web page."


Don't worry if you don't understand some of that - the main point is that you are up and running, and you've written your first script. The journey has just started.

Move on to the Next Part -->

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