original http://doginthehat.com.au/2012/02/comparison-block-helper-for-handlebars-templates/

ifcond_helper.js

'use strict';

(function() {
  /*jshint eqeqeq:false, maxparams:4 */

  var COND_OPERATORS = {
        '==' : function (l, r) { return l ==  r; },
        '===': function (l, r) { return l === r; },
        '!=' : function (l, r) { return l !=  r; },
        '!==': function (l, r) { return l !== r; },
        '<'  : function (l, r) { return l <   r; },
        '>'  : function (l, r) { return l >   r; },
        '<=' : function (l, r) { return l <=  r; },
        '>=' : function (l, r) { return l >=  r; },
        '%'  : function (l, r) { return l %   r; },
        'in' : function (l, r) {
          if (l.match(/^[0-9]+$/)) {
            l = parseInt(l, 10);
          }
          return r.indexOf(l) !== -1; },
        'typeof': function (l, r) {
          return typeof l == r;
        }
      };

  Handlebars.registerHelper('ifCond', function(lvalue, operator, rvalue, options) {

    var result;

    if (options === undefined) {
      options = rvalue;
      rvalue = operator;
      operator = '===';
    }

    if (arguments.length === 1) {
      if (lvalue) {
        return options.fn(this);
      } else {
        return options && options.inverse ? options.inverse(this) : '';
      }
    }

    if (!COND_OPERATORS[operator]) {
      throw new Error('Handlerbars Helper "ifCond" doesn\'t know the operator ' + operator);
    }

    result = COND_OPERATORS[operator](lvalue, rvalue);

    if (result) {
      return options.fn(this);
    } else {
      // TODO which case, why inverse is not defined?
      return options && options.inverse ? options.inverse(this) : '';
    }
  });

})();