1.3. What You Can Do with JavaScript JavaScript achieved early widespread use for simple tasks: validating form contents, or setting and retrieving cookies (small bits of information that persist even when the browser is closed). In the late 1990s, with the introduction of Dynamic HTML (DHTML), JavaScript was also used to provide a more dynamic user experience through drop-down menus and the like. JavaScript's popularity has grownexploded, reallymost recently because it is a key component in Ajax (Asynchronous JavaScript and XML), which promises to restructure the way web applications interact with users. Over time, many cross-platform problems have been resolved, and the language has become more sophisticatedso much so that JavaScript is no longer just a scripting language; it's a full-featured programming language. So what can you do with JavaScript? Well, for starters:
Validate form fields -
Validate form input before submitting the contents to the server. This saves time and server resources, and provides immediate feedback.
Set and retrieve web cookies -
Persist information such as usernames, account numbers, or preferences in a controlled, safe environmentsaving users time the next time they access a site.
Dynamically alter the appearance of a page element -
Provide feedback by highlighting incorrect form entries; increase the size of a section's font based on the reader's request.
Hide and show elements -
Based on personal preference or user actions, show or hide page content, such as form elements, expanding writing, and changing the displayed size of an image.
Move elements about the page -
Create a drop-down menu, or provide an animated cursor to accent page elements.
Capture user events and adjust the page accordingly -
Based on keyboard or mouse actions, make a section of the page editable.
Scroll content -
For larger images or content areas, provide a way to grab the element with a mouse or keyboard, and scroll it right or left, up or down.
Interface with a server-side application without leaving the page -
This is the basis of Ajax and is used to populate selection lists, update data, and refresh a displayall without having to reload the page. This helps eliminate round trips to the server, which can be costly in both time and resources. What can you do? Perhaps the better question is what can't you do. |
