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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Hello Ajax World!
You can use Ajax to populate a drop-down box based on a selection in another box. It’s an on-demand solution that limits how often a database is accessed. It’s also a very simple Ajax effect to create.
Example
13-1 contains the web page, including the script used to make the
Ajax server call. The page also contains a form with two select elements: one populated with two
states, the other empty.
Example 13-1. First Ajax application
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html> <head> <title>Hello Ajax World</title> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <style type="text/css"> div.elem { margin: 20px; } </style> <script type="text/javascript"> //<![CDATA[ var xmlhttp = false; if (window.XMLHttpRequest) { xmlhttp = new XMLHttpRequest( ); xmlhttp.overrideMimeType('text/xml'); } else if (window.ActiveXObject) { xmlhttp = new ActiveXObject("Microsoft.XMLHTTP"); } function populateList( ) { var state = document.forms[0].elements[0].value; var url = 'ajax.php?state=' + state; xmlhttp.open('GET', url, true); xmlhttp.onreadystatechange = getCities; xmlhttp.send(null); } function getCities( ) { if(xmlhttp.readyState == 4 && xmlhttp.status == 200) { document.getElementById('cities').innerHTML = "<select>" + xmlhttp.responseText + "</select>"; } else { document.getElementById('cities').innerHTML = 'Error: preSearch Failed!'; } } //]]> </script> </head> <body> <h3>Select ...Become 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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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.
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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.