main.js

module.exports = function (Handlebars) {
  /*! ******************************
    Handlebars helpers
    *******************************/
  
  // debug helper
  // usage: {{debug}} or {{debug someValue}}
  // from: @commondream (http://thinkvitamin.com/code/handlebars-js-part-3-tips-and-tricks/)
  Handlebars.registerHelper("debug", function(optionalValue) {
    console.log("Current Context");
    console.log("====================");
    console.log(this);
   
    if (optionalValue) {
      console.log("Value");
      console.log("====================");
      console.log(optionalValue);
    }
  });
  
  
  //  return the first item of a list only
  // usage: {{#first items}}{{name}}{{/first}}
  Handlebars.registerHelper('first', function(context, block) {
    return block(context[0]);
  });
  
  
  
  // a iterate over a specific portion of a list.
  // usage: {{#slice items offset="1" limit="5"}}{{name}}{{/slice}} : items 1 thru 6
  // usage: {{#slice items limit="10"}}{{name}}{{/slice}} : items 0 thru 9
  // usage: {{#slice items offset="3"}}{{name}}{{/slice}} : items 3 thru context.length
  // defaults are offset=0, limit=5
  // todo: combine parameters into single string like python or ruby slice ("start:length" or "start,length")
  Handlebars.registerHelper('slice', function(context, block) {
    var ret = "",
        offset = parseInt(block.hash.offset) || 0,
        limit = parseInt(block.hash.limit) || 5,
        i = (offset < context.length) ? offset : 0,
        j = ((limit + offset) < context.length) ? (limit + offset) : context.length;
  
    for(i,j; i<j; i++) {
      ret += block(context[i]);
    }
  
    return ret;
  });
  
  
  
  
  //  return a comma-serperated list from an iterable object
  // usage: {{#toSentence tags}}{{name}}{{/toSentence}}
  Handlebars.registerHelper('toSentence', function(context, block) {
    var ret = "";
    for(var i=0, j=context.length; i<j; i++) {
      ret = ret + block(context[i]);
      if (i<j-1) {
        ret = ret + ", ";
      };
    }
    return ret;
  });
  
  
  
  //  format an ISO date using Moment.js
  //  http://momentjs.com/
  //  moment syntax example: moment(Date("2011-07-18T15:50:52")).format("MMMM YYYY")
  //  usage: {{dateFormat creation_date format="MMMM YYYY"}}
  Handlebars.registerHelper('dateFormat', function(context, block) {
    if (window.moment) {
      var f = block.hash.format || "MMM Do, YYYY";
      return moment(Date(context)).format(f);
    }else{
      return context;   //  moment plugin not available. return data as is.
    };
  });
};