短小精捍的 javascript template engine

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 ):

// 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 ( /[ \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:

<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] ) ;
}