Live Comment Preview In Three Easy Steps

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Several people have complimented the live comment preview used in my skin. Try leaving a comment and notice the preview mode underneath. It now even supports a few HTML tags. Unfortunately I haven’t updated the comment page to tell you which tags are supported. Doh!

I did not write the original script. It was borrowed from the Asual Theme for blojsom and used in our Piyo skin.

However as I like to do, I spent a little bit of time trying to improve the script and turn it into a Markup Based Javascript Effect Library.

Now, by simply referencing this script, you can add live comment preview to any blog in three easy steps.

  1. Reference the script.
  2. Add the CSS class livepreview to a TextArea
  3. Add the CSS class livepreview to a div

The textarea is of course the form input into which the user enters a comment. In ASP.NET it would be a TextBox control with the TextMode property set to MultiLine like so:

<asp:TextBox id="tbComment" runat="server"\  Rows="10" Columns="40" width="100%" Height="193px"\ TextMode="MultiLine" class="livepreview"></asp:TextBox>

The <div> is the tag used to display the preview. There is a good reason to choose a div as opposed to allowing a <p> which I will talk about later. In my blog, that div already had a CSS class applied so I simply added the livepreview class like so:

<div class="commentText livepreview"></div>

And that’s it!

Well not exactly. I fibbed just slightly. There is actually a fourth step for the discriminating blog author. If you crack open the script, you’ll notice the following section on top:

var subtextAllowedHtmlTags = new Array(7);
subtextAllowedHtmlTags[0] = 'a';
subtextAllowedHtmlTags[1] = 'b';
subtextAllowedHtmlTags[2] = 'strong';
subtextAllowedHtmlTags[3] = 'blockquote';
subtextAllowedHtmlTags[4] = 'i';
subtextAllowedHtmlTags[5] = 'em';
subtextAllowedHtmlTags[6] = 'u';

In the next version of Subtext, that snippet is actually generated within an ASP.NET page (specifically DTP.aspx) as it is a list of HTML tags allowed by the blog engine. Since this is configured on the server, I needed some easy way to pass that information to the javascript. I chose to dynamically render javascript. I could have used an AJAX approach, but why bother at this point?

You can edit that array to specify your own tags. Note the preview only currently renders tags that contain something between a start and end tag. So for example, <b></b> won’t show up, but <b>Text</b> will.

For example if you add hr to your list of allowed tags, <hr /> won’t get rendered properly in the live comment preview. It will get rendered properly when it is actually posted as a comment. This may change in a future release.

Now it is up to you to apply some CSS styling to actually make the preview look good.

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