I'm working on a web site that allows people to enter RSS urls. These urls get parsed (via CFFEED) and displayed on a custom page. While I have support for handling bad RSS feeds, I wanted to create a quick demo where I'd use jQuery and ColdFusion to handle checking the RSS feeds while the user is working on the form. Here is what I came up with.

First - let's look at the form. The first two fields aren't really relevant. I added them to show that the RSS parsing was part of a greater form. The last three fields, the RSS labeled ones, are the fields we will care about.

<style> .rssfield { width: 500px; } .rssstatus { font-style: italic; } </style>

<form> name: <input type="text" name="name"><br/> max num of entries: <input type="text" name="maxentries"><br/> rss feed: <input type="text" name="rssfeed1" class="rssfield"><br/> rss feed: <input type="text" name="rssfeed2" class="rssfield"><br/> rss feed: <input type="text" name="rssfeed3" class="rssfield"><br/> <input type="submit"> </form>

Note that I've made use of a class, "rssfield", that is common to all the fields. This is going to come into play within our jQuery. And speaking of that - let's take a look at the JavaScript.

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script> <script> $(document).ready(function() {

$(".rssfield").blur(function() {
	var value = $(this).val()
	var name = $(this).attr("name")
	console.log('current value is '+value+' for field '+name)
	value = $.trim(value)

	//If blank, just quit - but clear any previous status		
	if(value == '') {
		if($("#status"+name).length == 1)  $("#status"+name).text("")
	//create a response span - if we don't have one
	if($("#status"+name).length == 0) $(this).next().before('&lt;span class="rssstatus" id="status'+name+'"&gt;Checking RSS validity...&lt;/span&gt;')
	else $("#status"+name).text("Checking RSS validity...")

	//call the server to check the field

	$.get('checkrss.cfm', { "rssurl":value}, function(data,status,eq) {
		if(data.verified == 0) {
			$("#status"+name).html("RSS value not valid: "+data.message)
		} else {
			$("#status"+name).html("RSS value valid!")

}) </script>

So as you can see - the bulk of the code here revolves around a blur handler for any field with the rssfield class. (I should probably have filtered it INPUT tags as well.) I begin by getting the value and name. Once I have the value, I do a quick trim on it. Now the first thing I want to do is ensure the user actually typed something in. If they didn't, I might as well leave. For now ignore that first line in the clause. It will make more sense in a second.

If the user did type something, I begin by creating a new span to handle a status message. Why did I do this? My thinking was - it would be kind of nice if I didn't add stuff to my form that was distracting. Not that a empty span would even register to a user, but I thought it would be nice if jQuery handled that as well. So essentially - I try to get a span for my particular field. If it doesn't exist, I create it. If it does exist, I set the text. I'm way open to being argued about this way of doing this.

Finally we get to the AJAX call. I pass the value to a ColdFusion script and then wait around the result. I'm going to expect a structure back. That structure will have two fields: verified and message. The message field will only be used for errors. So that's it really for the client side code, now let's take a look at checkrss.cfm:

<cfparam name="url.rssurl" default=""> <cfif url.rssurl is ""> <cfabort> </cfif>

<!--- Return a structure: verified: 0/1 (true/false) message: Only useful on bad results ---> <cfset result = {}> <cfif not isValid("url", url.rssurl)> <cfset result["verified"] = 0> <cfset result["message"] = "Value was not a valid URL."> <cfelse> <cftry> <cffeed source="#url.rssurl#" query="foo"> <cfset result["verified"] = 1> <cfset result["message"] = ""> <cfcatch> <cfif cfcatch.message is "Unable to parse the feed: Either source specified is invalid or feed is malformed."> <cfset result["verified"] = 0> <cfset result["message"] = "URL was not a valid RSS feed."> <cfelse> <cfset result["verified"] = 0> <cfset result["message"] = "Unable to verify RSS feed. Gremlins."> </cfif> </cfcatch> </cftry> </cfif>

<cfcontent type="application/json" reset="true"><cfoutput>#serializeJSON(result)#</cfoutput>

Stepping through - we being with a quick param for url.rssurl. If it is blank, we abort the request. Then we first check to see if the URL is valid. If not, we return a struct with a message saying that it was not. Now unfortunately, cffeed does not support a way to see if a URL is a valid RSS feed. So because of that, I perform the request and simply try/catch it. I've got one catch set up for a bad feed, and another set up for "everything else". Finally I serialize the response.

All in all - a pretty simple example. I do want to point out something. The jQuery form validation plugin (when I say "the" I obviously mean, to me, the best one) actually supports operations like this. You can easily set up validation rules that include hitting server side stuff for complex logic. I chose not to use it in this example because I'm not quite sure I'll be using the plugin for the site in question. And I wanted to write it myself for fun.

I've got a demo set up (see big ole button below), but unfortunately, I had to hobble it a bit. Any valid URL will be converted to http://feeds.feedburner.com/RaymondCamdensColdfusionBlog, which means it will always come back as true. I will explain why later today. (Possible new bad bug in cffeed unfortunately.)