What JavaScript can and cannot do.

JavaScript can add items such as:

• Scroling messages
• Animations and dynamic images
• Data input forms
• Pop-up windows
• Interactive quizzes

Javascript cannot be used to create applets or stand alone applications.

Back to top

JavaScript vs. Java: What's the difference?

Java is a full fleged object oriented programming language which allows you to create stand alone applications. Java is also used to create a special type of mini application called an applet. JavaScript is an interpreted languange, meaning it doesn't end up as an executable file.

Back to top

The advantages and disadvantages of using JavaScript.

Using JavaScript enhances a Web page by adding interactivity. Users can provide instant feedback without complicated CGI scripts and languages. JavaScript is supported by recent browsers from Netscape and Microsoft. Because Internet Explorer supposts additional features, Microsoft calls its version Jscript. Many old browsers are unable to handle newer JavaScript codes.

Back to top

The structure and use of variables, including naming conventions and variable types.

Rules for naming variables

• The name must begin with a letter or an underscore
• The rest of the name is made up of letters, numbers, or underscores
• Avoid naming variables with reserved words. For more information click here
• Do not place any spaces or punctuation in the name

Back to top

The difference between variables and literals.

A variable represents a value stored in memory for use by the script. A literal is an actual number or character text, rather than a calculated result or value input from a keyboard.

Back to top

How to set up expressions, including the rules for the order of precedence.

An expression operates by taking the values to the right hand side of the equal sign, performing the arithmic operation, and then storing the result in the variable on the left hand side of the equal sign.

Mathematical order of Precedence

• Parentheses, with innermost parentheses first ()
• Increment and decrement ++ and --
• Multiplication, division, and modules *,/, and %
• Addition and subtraction + and -

Back to top

Conditionals

To validate data entered into a form you compare or test the data entered to a desired value. This test is called a conditional, and the result of the test is either True or False. Based on the result of the test you can execute different JavaScript codes.

Back to top

Functions

A funtion is a way to write several lines of script and use them repeatedly as nested. Functions are defined by starting with the keyword function followed by a set of parentheses.

Back to top

Objects, properties, and methods

• An object is a real-world entity. JavaScript makes use of objects in its association with Web browsers. This technique is called object orented (OO). When it refers to programming it is called Object Oriented Programming (OOP).
• An object is described bu its properties. Properties are attributes that help differentiate one object from another.
• A behavior is called a method. A method is a function or action you want the object to perform.

Back to top

Events and event handlers

Most interactive Web applications are event-driven

• An event is an action that occurs, such as a user clicking a link or buton, or a user entering data in a form textbox.
• For JavaScript to react to an event, event handlers must be written.

Back to top

Dynamic use of frames

A frame is a feature that allows a browser window to be split into smaller units. These units are not windows.

Back to top

Arrays

An array is a collection of data intems that is identified by a singular name. The singular name is used in place of many different variables that would have to be used if JavaScript did not have the capability of using arrays.

Back to top