spacer
Yehuda Shiran January 15, 2002
Restoring Cookies in Persistent Related Menus
Tips: January 2002

Yehuda Shiran, Ph.D.
Doc JavaScript

Developer News
Microsoft Shows Off Silverlight 4, IE9 Plans
Metasploit Expands Vulnerability Test Framework
HyperCard Reborn?

 One of the problems of related menus is that once you visit another Web page and then come back, the menu selections tend to change. You can overcome this problem with cookies. The cookie property belongs to the document object. Play around with these related menus:

Write down the entries you see on both menus. Let's assume that the left and right menus are level2 and level23, respectively. Now, surf to another Web site of your choice. Hit the browser's Back key. You will see that both menus have retained the entries of .level2 for the left menu and level23 for the right menu.

The trick is to save the menu index in a cookie whenever it changes, and restore the cookie upon the page's reloading. We save the cookie when the right menu ("list") changes, under the name of listSelectedIndex.

We restore the cookie when the page loads. Actually, we need to do more than that. The selected index of the left menu persists by itself, so we need to adjust again the right menu accordingly. If the left menu is level2, for example, the right menu should present the options level21, level22, and level23. The particular option that needs to be selected out of these three is read from the restored cookie.

Let's see how we reflect this business logic in our code. First, we add the onLoad event handler to the <BODY> tag:

<BODY onLoad="refreshOnDocLoad()">
The refreshOnDocLoad() function just calls the relate() function with the first form of the page:

function refreshOnDocLoad() {
  relate(document.forms[0]);
}
The relate() function first initialized the options of the right menu to null:

  var options = form.list.options;
  for (var i = options.length - 1; i > 0; i--) {
    options[i] = null;
  }
Then, it assigns the relevant options from the left menu:

  var curAr = ar[form.topics.selectedIndex];
  for (var j = 0; j < curAr.length; j++) {
    options[j] = new Option(curAr[j].text, curAr[j].url);
  }
Now, it reads the cookie:

  var indexOfSelectedOption = getCookie("listSelectedIndex");
We just need to make sure the cookie is not empty. If it is, we select the first option. If it is not empty, we use its contents to pick the selected index:

  if (indexOfSelectedOption != null) {
    options[indexOfSelectedOption].selected = true;
  } else {
      options[0].selected = true;
    }

People who read this tip also read these tips:

Look for similar tips by subject:

internet.commediabistro.comJusttechjobs.comGraphics.com

Search:

WebMediaBrands Corporate Info

Legal Notices, Licensing, Permissions, Privacy Policy.
Advertise | Newsletters | Shopping | E-mail Offers | Freelance Jobs

Solutions

Whitepapers and eBooks

Microsoft Articles: Visual Studio 2010
Adobe Article: Adobe Helps PHP Developers Create Rich Internet Applications
Microsoft Whitepaper: How Windows Server 2008 R2 Helps Optimize IT and Save You Money
Adobe Article: Java Developers Finding a Home at Adobe Flex
IBM Articles: A Smarter Business Needs Smarter Technology
Intel Xeon Processor Increases Server Efficiency and Capabilities
Intel Tech Brief: Automated Energy Efficiency for the Intelligent Enterprise
Oracle Whitepapers - Innovation for IT Leaders
Avaya Article: Communication-Enabled Mashups--Empowering Both Business Owners and IT
 Internet.com eBook: IT Manager's Guide to Social Networking
Internet.com eBook: Get Ready for Windows 7
Microsoft Article: Expression Web 3--New Features for PHP Developers
Whitepapers: Manage Your Business Infrastracture with IBM
Whitepaper: Maximize Your Storage Investment with HP
Internet.com eBook: Becoming a Better Project Manager
Microsoft Article: Stress Free and Efficient Designer/Developer Collaboration
MORE WHITEPAPERS, EBOOKS, AND ARTICLES

Webcasts

Webcast: Connecting PHP to Microsoft Technologies
Video: Microsoft Partner Program Benefits
Video: Windows Azure Debugging Tips
SAP BusinessObjects Webcast: Unlock the Power of Reporting with Crystal Reports
 IBM Webcast: Speed Business Innovation with Reduced Cost and Risk
Video: Deploy Applications on Windows Azure
MORE WEBCASTS, PODCASTS, AND VIDEOS

Downloads and eKits

Download: Microsoft Visual Studio 2010 Beta 2
Downloads & Free Trials: Microsoft's New Efficiency Resource Center
Get the Windows 7 SDK
 Free Trial: Red Gate SQL Backup Pro 6
Iron Speed Designer Application Generator
MORE DOWNLOADS, EKITS, AND FREE TRIALS

Tutorials and Demos

Internet.com Hot List: Get the Inside Scoop on the Hottest IT and Developer Products
All About Botnets
 MORE TUTORIALS, DEMOS AND STEP-BY-STEP GUIDES
webref The latest from WebReference.com Browse >
Rolling Out Your Own HTML Application Version Control · HTML 5: Client-side Storage · Working with Ajax Server Extensions
Sitemap · Experts · Tools · Services · Email a Colleague · Contact FREE Newsletters > 
 The latest from internet.com
Wi-Fi Product Watch, November 2009 · Chip Market Recovering From '08 Collapse · Low-Cost Tools to Kickstart Your New Business