A small template rendering engine in JS ... uses Function constructor, unfortunately

000-lessthan140chars.js

function(b,c){return b.replace(/{[\w\.\(\)]+}/g,function(a){a=a.replace(/[\{\}]/g,"");try{with(c)return eval(a)}catch(b){return""}})};

Example using twitters API

goto http://jsfiddle.net/netroy/HA8es/ for a running example using this renderer

NewTemplater.js

// Similar to the older version, without eval & with (sort-of)

function render(template, data) {
  return template.replace(/\{[\w\.\-\(\)]+\}/g, function(match){
    var token = match.replace(/[\{\}]/g,"");
    try {
      return (new Function("data", "return data." + token))(data);
    } catch(e) {
      return "";
    }
  });
}

OldTemplater.js

// templates support object & function ... like "{abcd}" or "xyz.pqr" or "GL.package.class.init(arguments.toString())"
// data is an object with values that would be used for rendering .... like {abcd:"something",xyz:{pqr:123},arguments:[]}

function render(template, data){
  return template.replace(/{[\w\.\-\(\)]+}/g, function(match){
    var token = match.replace(/[\{\}]/g,"");
    try {
      with(data) {
        return eval(token);
      }
    } catch(e) {
      return "";
    }
  });
}

Supplants can do this task

/* Supplant */
if(typeof String.prototype.supplant !== 'function') {
    String.prototype.supplant = function(o) {
        return this.replace(/{([^{}]*)}/g,
            function (a,b) {
                var r = o[b];
                return typeof r === 'string' ?
                    r : a;
            });
    };
}

You need a template and data

template = "this is {data}  "
data = {"data" : "value"}
result = template.supplant(data);

wouldn't work for nested objects like ...

template = "{user.name} is {user.age} years old"
data = {"user": {"name":"X", "age": 99}}

this was supposed to show that eval isn't all that unnecessary, if you understand the risks involved

You can consider timeago plugin for awesome time stamps. Don't have to code yourself.

Read through the fiddle sample. Nice :) Can we get rid of eval somehow? Will try to update supplants to handle this feature.

As of ES5, eval executes in a private scope, so its okay to use it if needed.
More important thing to remove is the with statement, but without that, i haven't figured out how to have function calls in templates.
for just namespaced objects, with can be replaced by a eval("data."+token)

Will have to dig more into this. I got the above snippet from Crockford