Comment Preview Using MooTools

Comment previewing is an awesome addition to any blog. I've seen really simple comment previewing and some really complex comment previewing. The following is a tutorial on creating very basic comment previewing using MooTools.

The XHTML

<div id="live-preview-form" class="lp-block">
	<p>
		<strong>Your Name:</strong><br />
		<input type="text" name="name" id="name" value="" class="input" /><br /><br />
		<strong>Your Email:</strong><br />
		<input type="text" name="email" id="email" value="" class="input" /><br /><br />
		<strong>Your Website:</strong><br />
		<input type="text" name="website" id="website" value="" class="input" /><br /><br />
		<strong>Your Comment:</strong><br />
		<textarea name="comment" id="comment" class="input" rows="10"></textarea>
	</p>
</div>

<div id="live-preview-display" class="lp-block">
	<div id="lp-avatar"></div>
	<div id="lp-name"></div>
	<div id="lp-comment"></div>
</div>

You can set up your XHTML any way you'd like. It's important for the sake of consistency to make your preview display look as closely as possible to your real comments display.

The CSS

.lp-block		{ width:400px; float:left; }
.lp-block input, .lp-block textarea { width:90%; }
#live-preview-display 	{ background:#eee; padding:10px; margin-left:50px; margin-top:20px; }

#lp-name { font-weight:bold; }
#lp-avatar { float:right; margin:0 0 20px 20px; }
#lp-comment { padding-top:10px; font-style:italic; line-height:19px; }

Make your "preview" CSS look just like your real comments display.

The MooTools JavaScript

(function($){
	window.addEvent('domready',function(){
		//the build process
		var build = function() {
			//vars (fields) and blocks
			var lpcomment = $('lp-comment'), lpname = $('lp-name'), lpavatar = $('lp-avatar');
			var name = $('name'), email = $('email'), website = $('website'), comment = $('comment');
			
			//comment
			lpcomment.set('text',comment.value);
			lpcomment.set('html',lpcomment.get('html').replace(/\n/g,'<br />'));
			
			//name & websites
			if(website.value && (website.value).test(/http:\/\/[A-Za-z0-9\.-]{3,}\.[A-Za-z]{2}/)) {
				lpname.set('html','<a href="' + website.value + '">' + name.value + '</a> says:');
			}
			else {
				lpname.set('text',name.value + ' says:');
			}
			//gravatar
			if(email.value && (email.value).test(/^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/)) {
					var md5Email = MD5(email.value);
					lpavatar.set('html','<img src="http://www.gravatar.com/avatar.php?gravatar_id=' + md5Email + '&size=80&rating=G&default=http%3A%2F%2Fdavidwalsh.name%2Fwp-content%2Fthemes%2Fdavid-walsh%2Fgraphics%2Fcom.jpg" />');
			}
		};
		//comment...easy
		$$('#live-preview-form input, #live-preview-form textarea').addEvents({
			keyup: build,
			blur: build
		});
	});
})(document.id);

The JavaScript is quite easy. Note that I'm doing very basic validation and formatting -- you may get as fancy or simple as you'd like. Also note that I'm using an MD5 function for the gravatar functionality. The MD5 function was found here.

This is as basic as it gets. You may want to implement functionality that checks for valid URLs and email addresses. You may also want to implement a regular expression that turns two line breaks into </p><p> tags. If you'd like to implement a more sophisticated system, I highly recommend using Thomas Aylott's SubtleTemplates.