Nutshell

Here a small example of a Jinja template:

{% namespace ns1 %}

{% macro printusers(users) %}
<ul>
{% for user in users %}
    <li><a href="{{ user.url }}">{{ user.username }}</a></li>
{% endfor %}
</ul>
{% endmacro %}

Which after running through the pwt.jinja2js compiler we need up the following JavaScript:

if (typeof ns1 == 'undefined') { var ns1 = {}; }

ns1.printusers = function(opt_data, opt_sb, opt_caller) {
   var output = '';
   output += '\n<ul>\n';
   var userList = opt_data.users;
   var userListLen = userList.length;
   for (var userIndex = 0; userIndex < userListLen; userIndex++) {
       var userData = userList[userIndex];
       output += '\n   <li><a href="' + userData.url + '">' + userData.username + '</a></li>\n';
   }
   output += '\n</ul>\n';
   return output;
}

By slipping a switch we can produce Java Script that takes advantage of Closure Library:

goog.provide('ns1');

goog.require('soy');

ns1.printusers = function(opt_data, opt_sb) {
   var output = opt_sb || new soy.StringBuilder();
   output.append('\n<ul>\n');
   var userList = opt_data.users;
   var userListLen = userList.length;
   for (var userIndex = 0; userIndex < userListLen; userIndex++) {
       var userData = userList[userIndex];
       output.append('\n   <li><a href="', userData.url, '">', userData.username, '</a></li>\n');
   }
   output.append('\n</ul>\n');
   if (!opt_sb) return output.toString();
}