handlebars-helpers.js

/*! ******************************
  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: {{#toSentance tags}}{{name}}{{/toSentance}}
Handlebars.registerHelper('toSentance', 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.
  };
});