Ajax is great. Of that there's little doubt. However, it has to be used carefully in order to be most effective. In particular we need to make sure its use does not impeed users for whom it might not work.

A lot of the projects I've been involved in recently have required a degree of accessibility built in. Rather than deny the majority of users the funkiness that using Ajax can provide I've come up with a way to use a single Domino form to provide simple functionality to both Ajax actions as well as traditional methods. This article is going to look at how I did that.

Ajax is best and most often used for the simple little tasks. For example, something like adding a vote to a poll is an ideal situation to which Ajax is suited.

Imagine you were reading a document on which a vote is being taken. It might include a Vote Here link which looks something like this:

It looks innocent enough, but there's a problem with this link. Once the doVote() function has run the link will still be followed and the user will end up at reloading the page at the same URL but with an empty hash (#) at the end of it.

To prevent this the link should look like this:

Now the doVote() function runs and then the click of the link is effectively cancelled by returning a false statement.

If you're going to link to JavaScript calls in the onclick event of a link. Always make sure your return false after the function call!

The link is now less prone to error but there's still a problem with it. Imagine either the doVote() function causes an error — for whatever reason — or that the user has no JavaScript capability — again, for whatever reason. What do we do now?

What I've started doing and what I propose we all do from now on is cater for all cases with a link that looks something like this:

Now, when there's no JavaScript support or when an error occurs in the JavaScript it fails-over to a good old fashioned link. In effect the two methods do the same thing. All that the doVote() function does is POST to the "vote" form and pass same value to it. Here's what the code might look like (based on Mootools here, but would be the same when using most of the libraries):

function doVote(vote){
 new Ajax(
  'vote?CreateDocument', 
   {
    method: 'post', 
    data: {'vote':vote, 'ajax':'true'}, 
    onComplete:function(response){
     $('vote_link').innerHTML=response;
    }
   }
  ).request();
} 

We're still creating a vote "form" and passing it the vote. The only difference is that we tell the form that Ajax was used. Using the information the WQS agent of the Vote form knows whether to simply return some text to the browser or to perform a redirect.

The Vote form itself is just a place holder really. It doesn't store documents (SaveOptions="0"). All it does is capture the values passed to it and then make them easily available to the WebQuerySave agent that runs. We could pass the data straight to an agent but parsing it in LotusScript is a nightmare and it's much better to let a Form do it. As well as the data passed to it we can use the Form to compute other information such as the user name, path info etc.

Fields on the form to which data are passed are auto-filled by the POST action of the Ajax request. However, when we use a ?CreateDocument GET request we have to fill the fields ourselves. To do this we set their Default Values using @URLQueryString calls to grab data from the URL.

Taking Further

What next?

Demo Database

DEMO HERE -- Download link is on the right towards to the top.

To Do On This Article

• Talk about side-effect of web crawlers following links like this. Rel=nofollow?