I've had a little utility that I've been kicking around for some time now that I've found to be quite useful in my JavaScript application-building endeavors. It's a super-simple templating function that is fast, caches quickly, and is easy to use. I have a couple tricks that I use to make it real fun to mess with.
Here's the source code to the templating function (a more-refined version of this code will be in my upcoming book Secrets of the JavaScript Ninja):
// Simple JavaScript Templating // John Resig - http://ejohn.org/ - MIT Licensed (function(){ var cache = {}; this.tmpl = function tmpl(str, data){ // Figure out if we're getting a template, or if we need to // load the template - and be sure to cache the result. var fn = !/W/.test(str) ? cache[str] = cache[str] || tmpl(document.getElementById(str).innerHTML) : // Generate a reusable function that will serve as a template // generator (and which will be cached). new Function("obj", "var p=[],print=function(){p.push.apply(p,arguments);};" + // Introduce the data as local variables using with(){} "with(obj){p.push('" + // Convert the template into pure JavaScript str .replace(/[ ]/g, " ") .split("<%").join(" ") .replace(/((^|%>)[^ ]*)'/g, "$1 ") .replace(/ =(.*?)%>/g, "',$1,'") .split(" ").join("');") .split("%>").join("p.push('") .split(" ").join("\'") + "');}return p.join('');"); // Provide some basic currying to the user return data ? fn( data ) : fn; }; })();
You would use it against templates written like this (it doesn't have to be in this particular manner - but it's a style that I enjoy):
<script type="text/html" id="item_tmpl"> <div id="<%=id%>" class="<%=(i % 2 == 1 ? " even" : "")%>"> <div class="grid_1 alpha right"> <img class="righted" src="<%=profile_image_url%>"/> </div> <div class="grid_6 omega contents"> <p><b><a href="/<%=from_user%>"><%=from_user%></a>:</b> <%=text%></p> </div> </div> </script>
You can also inline script:
<script type="text/html" id="user_tmpl"> <% for ( var i = 0; i < users.length; i++ ) { %> <li><a href="<%=users[i].url%>"><%=users[i].name%></a></li> <% } %> </script>
Quick tip: Embedding scripts in your page that have a unknown content-type (such is the case here - the browser doesn't know how to execute a text/html script) are simply ignored by the browser - and by search engines and screenreaders. It's a perfect cloaking device for sneaking templates into your page. I like to use this technique for quick-and-dirty cases where I just need a little template or two on the page and want something light and fast.
and you would use it from script like so:
var results = document.getElementById("results"); results.innerHTML = tmpl("item_tmpl", dataObject);
You could pre-compile the results for later use. If you call the templating function with only an ID (or a template code) then it'll return a pre-compiled function that you can execute later:
var show_user = tmpl("item_tmpl"), html = ""; for ( var i = 0; i < users.length; i++ ) { html += show_user( users[i] ); }
The biggest falling-down of the method, at this point, is the parsing/conversion code - it could probably use a little love. It does use one technique that I enjoy, though: If you're searching and replacing through a string with a static search and a static replace it's faster to perform the action with .split("match").join("replace") - which seems counter-intuitive but it manages to work that way in most modern browsers. (There are changes going in place to grossly improve the performance of .replace(/match/g, "replace") in the next version of Firefox - so the previous statement won't be the case for long.)
Feel free to have fun with it - I'd be very curious to see what mutations occur with the script. Since it's so simple it seems like there's a lot that can still be done with it.