July 2010
Intermediate to advanced
552 pages
12h 40m
English
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Chapter 7. Handling Events
7.0. Introduction
Events, especially within an interactive environment such as a browser, are what make JavaScript essential. There is very little JavaScript functionality that isn’t triggered by some event, even if the only event that occurs is a web page being loaded. Event handling in JavaScript depends on determining which event or events you want to trigger some activity, and then attaching JavaScript functionality to the event.
The earliest form of event handling is still one of the most common:
the use of an event handler. An event handler is an element property that
you can assign a function, such as the following, which assigns a function
to the window.onload event
handler:
window.onload=someFunction;
You can also assign an event handler directly in an element, such as
in the opening body tag:
<body onload="someFunction()">
However, I don’t recommend embedding events directly in page elements, as it makes it difficult to find and change the event handling routines later. If you use the first approach, which is to assign a function to an event handler in script element or in a JavaScript library, you only have to look in one place in order to make changes.
Note
JavaScript lives in an enormous number of environments, as Chapter 21 demonstrates. Most of this chapter is focused on JavaScript within a browser or browser-like environment.
Some Common Events
There are several events that can be captured via JavaScript, though not all are available to all web page ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.