Assemble - Handlebars.js でヘルパーからオブジェクトを参照する ref: http://qiita.com/tkdn/items/499d253c0c71ebdaf56b

custom-helper.js

module.exports.register = function (Handlebars, options, params) {
  'use strict';
  Handlebars.registerHelper('foo', function(str) {
    return str;
  });
};

custom-helper2.js

  Handlebars.registerHelper('buz', function(str1, str2) {
    var value = "";
    for(i=0;this.pages.length>i;i++){...}
    return val;
  });

file0.html

{{#each pages}}
  <li>{{dest}}</li>
{{/each}}

file1.yml

date: "2015-02-14"
title: "valentine's day"

file2.html

{{#each pages}}
  <li>{{dest}} - {{../title}}</li>
{{/each}}

file6.js

return new Handlebars.SafeString(str);