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JavaScript is a well-established scripting language which creates code that can execute both an HTML page loads and after it has loaded. It is very efficient since it can run independently on the computers of the visitors to your web site. Thus freeing up your server to do other things. It is so widely used on web sites that, though it is possible for a user to disable JavaScript within their browser settings, most people will need to leave it active if they are to interact with the sites they visit. Adobe Dreamweaver allows web developers to add JavaScript to their pages by using what it refers to as “behaviors”.

Behaviors are editable Dreamweaver resources which generate one or more JavaScript functions. Each behavior needs to be associated with an element on your web page. After highlighting the element, you click on the Window menu and choose Behaviors. In the top left of the Behaviors window, you then click on the Add Behavior button an icon which looks like a plus sign (+). Choose on of the available behaviors to associate it with the highlighted element.

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 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.

In the alerts and windows category, we have Dreamweaver’s “Open Browser Window” behavior. This creates the ever-popular pop-up window. When you assign the behavior, Dreamweaver asks you to choose the HTML page you would like displayed in the window as well as the attributes you would like to add or suppress, such as scroll bars or the ability to resize the window.

The key behavior relating to forms is called “Validate Form”. It performs simple checks on any text field within a given form. (It ignores any fields other than text fields.) To use it, select a field (the validation will then occur when the user leaves the field) or select the entire form (the validation will then occur when the form is submitted). Choose “Validate Form” form the Behaviors panel menu and specify the type of validation you wish to perform, for example, ensuring that a field has not been left blank.

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.

If you have used several JavaScript behaviors on a page, you may find that the amount of code generated by Dreamweaver becomes quite significant. It is therefore usually a good idea to place all of this code in an external JavaScript file and then link this file to your page. To do this, click on the “Code” button in the top left of the page and locate the SCRIPT tags which contain the JavaScript. Select all of the code between the SCRIPT tags and cut it to the clipboard. Next, create a blank file with the file extension .js and paste all of the code inside it. Finally, to link your page to the .js file, position your cursor inside the opening SCRIPT tag and type src = “myfile.js” substituting the name of your JavaScript file for “myfile.js”.

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Tags: Software