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Chapter 4. Working with Images

One of the best uses of JavaScript is to add visual interest to Web pages by animating graphics, and that's what this chapter is all about. Making an image on a Web page change when the user moves the mouse over the image, thereby making the page react to the user, is one of the most commonand effectivetricks you can learn in JavaScript. This rollover, as it is called, is easy to implement, yet has many applications, as you'll see.

Rollovers are a great tool, but you can do much more than rollovers with JavaScript, such as automatically change images, create ad banners, build slideshows, and display random images on a page.

In this chapter, you'll learn how to make JavaScript do all of these image tricks. Let's get started.

Table 4.1. Just Enough HTMLImages






Contains the attributes that describe the image to be displayed by the browser



Contains the URL of the image, relative to the URL of the Web page



Contains the width (in pixels) at which the browser will display the image



Contains the height (in pixels) at which the browser will display the image



The width of the border to be displayed



The name that JavaScript uses to refer to this image; as with other JavaScript objects, no spaces or other punctuation is allowed, and it cannot start with a number



Used for non-visual browsers in place of the image



A horizontal buffer area around the image



A vertical buffer area around the image



Describes where this image should be placed on the page in terms of horizontal or vertical alignment



A unique identifier, which JavaScript will use to manipulate the image

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