Unobtrusive Javascript Example - Printing

May 29, 2007 · 2 minute read

In lieu of some real posts here’s a quick code sample to keep things ticking along.

I’m sure you’ve had the need to place a nice print button on a web page from time to time. If you haven’t you’re probably alone. A quick google will throw up lots of results for print javascript - the problem is that most of them are horribly obtrusive.

OK, so it’s easy to write something like:

<code><a href="#" onclick="window.print();">print</a></code>

But the problem is What if you turn off javascript? The following unobtrusive script automagically adds a print link to the page - in this case as part of a list item which is added to the unordered list with the id of iNav and a class of has-print.

<code>var Print = {
   init: new domFunction(function() {
      if (list = document.getElementById("iNav")) {
         if (list.nodeName.toLowerCase() === 'ul') {
            if (Print.hasClass(list,'has-print')) {
               var item = document.createElement("li");
               item.className = "print";
               var link = document.createElement("a");
               link.href = "#";
               link.onclick = Print.printpage;
               var txt = document.createTextNode("Print");
               link.appendChild(txt);
               item.appendChild(link);
               list.appendChild(item);
            }
         }
      }
   }),

   hasClass: function(element,cName) { 
      return new RegExp('\\b'&#43;cName&#43;'\\b').test(element.className);
   },

   printpage: function() {
      window.print();
      return false;
   }
}</code>

With something like this you want it to load as soon as the dom is ready, rather than on page load. Brothercake’s domFunction comes to the rescue here. The namespacing is based on Stuarts technique which should make it more capable of just being dropped in to any site.

The only problem with this is that it’s just a little longer than the original. I think this is down to one often missed fact, at least until recently - Javascript is a programming language and should be treated as such.