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JavaScript is an easy-to-use programming language which runs client-side (on each web surfer’s computer) and adds useful or decorative interactivity to web pages. No extra plug-ins need to be installed into the browser for JavaScript to run and, although it can be disabled by users to stop script running, it is safe to assume that any JavaScript code added to your pages will run on the vast majority of the computers of visitors to your site. Dreamweaver allows you to add JavaScript to your code automatically and easily by using “behaviors”.

A Dreamweaver behavior is an automatically generated JavaScript function which is activated by a given user or browser action. To use behaviors, choose Window > Behaviors. Before attaching a behavior, you must highlight one of the elements on your page such as a hyperlink or image. Then you need to choose a behavior by clicking on the plus sign in the top left of the Behaviors window.

You will also need to ensure that the correct event (click, double-click etc.) is linked to the behavior. Dreamweaver will always assign an event automatically. However, if this event is not the one you actually want, just select a different event by clicking on the drop-down menu located to the right of the name of the event in the Behaviors panel.

Dreamweaver contains several types of JavaScript behaviors. Some relate to images, others display windows and messages, others can be used on forms and form fields and still others can be used to manipulate CSS attributes. To get a flavour of how behaviors work, let us examine a behavior in each of the above 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.

Dreamweaver’s “Open Browser Window” behavior allows you to create the controversial JavaScript pop-ups. Due to its extensive misuse, many people have developed an extreme intolerance of this feature. However, there are situations where it is useful. For example, if a user is in the middle of filling out a form and clicks a help icon next to a certain item, a pop-up window is an ideal method of displaying the help topic.

In the form manipulation behaviors category, we have “Set Text of Text Field” and “Validate Form”. The “Validate Form” behavior only applies to text fields and enables you to ensure, first of all, that a field has not been left blank; secondly, that a field contains a valid email address; thirdly, that a field contains a numeric value; and, fourthly, that a field contains a number within a given range.

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 .

Filed under: Javascript