javascript templating
JavaScript Micro-Templating
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):
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// Simple JavaScript Templating(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(/[\r\t\n]/g, " ") .split("<%").join("\t") .replace(/((^|%>)[^\t]*)‘/g, "$1\r") .replace(/\t=(.*?)%>/g, "‘,$1,‘") .split("\t").join("‘);") .split("%>").join("p.push(‘") .split("\r").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:
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<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:
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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:
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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.
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