Introducing JavaScript

JavaScript notes on W3Schools.com

(This is self-study tutorial)

 

Chapter 7 JavaScript

Scripting vs. Programming Languages

A programming language may be used to create stand-alone programs. A scripting language is usually built into a specific application like a database or spreadsheet or webpage and cannot be used outside of that application.

JavaScript is a scripting language, not a full programming language. It is also not an outgrowth of the Java programming language.

Basic Idea of JavaScript

The web page designer adds JavaScript instructions directly into an HTML source document.

JavaScript may be added to the head, or to the body, of an HTML source document, but the effects are different!

The <script> Element

<script>
alert("Hello, world!")
</script>

Two types of comments

//This is a single-line comment

/* This is a multiple-line
comment */

Making a Web Page Safe for Non-JavaScript Browsers

<script type="text/javascript">
<!--
JavaScript code goes here.....
//-->
</script>

By doing this, non-JavaScript enabled browsers will ignore everything inside the comments. JavaScript enabled browsers are smart enough to ignore the first <!-- but correctly interprets the following codes. The free JavaScript codes you download are often written in such a way to be safe for non-JavaScript browsers. However new generation of XML/XHTML browsers may ignore everything inside comments tags!

Chapter 8 Objects and Variables

The dot Notation

objectName.propertyName

house.color

Object is 'house', its property is 'color'

Assignment Statement

house.color = "green"

The color of the house is green.

Variables

Variables must be declared before used.

<script type="text/javascript">
var answer
answer = 2.3
alert("answer is" + answer)
</script>


The above would create an alert box and display the text: answer is 2.3.

JavaScript's three types of data

strings, numbers and boolean

If statement

if (booleanPredicate)
{ executeThisIfTrue }
else
{ executeThisIfFalse }