JavaScript is a simple, client-side scripting language which enables you to add exciting and interesting functionality to your HTML pages. It is built in to most web browsers and, although it can be deactivated, most people will have it enabled within their browser. JavaScript’s uses includes the validation of entries within an HTML form and the detection of browser versions and presence or absence of plug-ins. Dreamweaver’s implementation of JavaScript centres on the use of what it calls “behaviors”.

A behavior is simply a pre-written JavaScript function which can be triggered by a given event. To make the Behaviors window visible, choose Behaviors from the Window menu. Next select the element to which you want to attach the JavaScript. Finally, choose one of the available behaviors from the menu in Behaviors window. (The behaviors which are available will depend on the item you have highlighted.)

Whenever you attach a behavior to a web page element, Dreamweaver attempts to guess what the event which should trigger the JavaScript (mouse click, rollover, etc.). If Dreamweaver fails to assign the event that you actually want, simply choose a different event from the drop-down menu next to the event name.

Dreamweaver has a wide selection of behaviors. However, they fall into four main categories: images, windows and alerts, forms and form fields and CSS. To see how behaviors work, let us look at some examples of some behaviors in each of those categories.

Perhaps the most frequently encountered JavaScript function is one that changes the appearance of an image when the mouse passes over it. Dreamweaver creates this functionality with the “Swap Image” behavior. You can also add this behavior automatically by choosing Insert – Image Objects – Rollover Image. Dreamweaver automatically adds a second behavior/function called “Restore Image” which changes the image back to the original when the mouse leaves the image.

As far as alerts and windows behaviors is concerned, as well as the simple “Pop-up Message”, which just causes a system alert box to appear, Dreamweaver also offers the more sophisticated “Open Browser Window”. This Dreamweaver behavior allows you to create a pop-up window of any specified dimension and allows you to choose the attributes of the window: the HTML file it displays, the presence or absence of the title bar, scroll bars, etc.

The most important and useful form-handling behavior is “Validate Form”. This can be triggered either on submission of the form (“onSubmit”) or when a given text field loses focus (“onBlur”). When you assign the behavior, you choose the type of validation you wish to perform: ensuring that the field has not been left blank, contains a valid email address, contains a number or contains a number between two specific values.

An example of a behavior which manipulates CSS attributes is “Show/Hide Elements”. This enables you to control the visibility of the content inside an HTML element, such as a DIV, heading or paragraph, based on user action. So, for example, when if you have a picture of a product, you can create DIVs with information on various aspects of the product and have the appropriate DIV content become visible as the user mouses over various parts of the product image.

Each behavior that you choose will create one or more JavaScript functions within the head area of your page. Part of the process of optimising your website (both in terms of accessibility and search engine compatibility) is to transfer this code to an external JavaScript file and then link the web page to the JavaScript file. To do this, you need to be in Code view and locate the function(s) generated by the behavior(s) you have used on your page. Cut all of the code between the opening and closing SCRIPT tags and place it in a text file which needs to be saved with a .js extension. Next, enter an src attribute inside the opening SCRIPT tag, for example ‘SCRIPT src=”scripts.js”‘.

You can find out more about JavaScript training courses, visit Macresource Computer Training, a UK IT training company offering JavaScript training courses at their central London training centre.

categories: Dreamweaver,Adobe Dreamweaver CS3,JavaScript,behaviors,web development,website accessibility,computers and the internet,computer software