October 2006
Beginner to intermediate
352 pages
9h 33m
English
Content preview from Learning JavaScriptBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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First Look at JavaScript: “Hello World!”
One reason JavaScript is so popular is that it’s relatively easy to add JavaScript to
a web page. All you need to do, at a minimum, is to include HTML script
tags in the page, provide the JavaScript language for the type attribute, and add whatever JavaScript
you want:
<script type="text/javascript"> ...some JavaScript </script>
Traditionally, script tags are added to the head element in the document (delimited by
opening and closing head tags), but
they can also be included in the body
element—or even in both sections.
Example
1-1 shows a complete, valid web page, including a JavaScript
block that uses the built-in alert
function to open a message box containing the “Hello, World!”
text.
Example 1-1. JavaScript block in the document head
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html> <head> <title>Example 1-1</title> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <script type="text/javascript"> var dt = Date( ); // say hello to the world var msg = 'Hello, World! Today is ' + dt; alert(msg); </script> </head> <body> </body> </html>
Copying this into a file and opening the file in any web browser should result in a box popping up as soon as the page as loaded. If it doesn’t, chances are that JavaScript is disabled in the browser, or, something very rare these days, that JavaScript isn’t supported.
Though the example is simple, it does expose ...
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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.