Handlebars If helper.

hbs_if_helper.js

Handlebars.registerHelper("if", function (expression, options) {
  try {
    if (expression.split(' ').length == 1 && (!/@(\w+)/.test(expression))) {
      if (options.data.root[expression] && !!(options.data.root[expression])) {
        return (options.data.root[expression]) ? options.fn(this) : options.inverse(this);
      } else {
        return options.inverse(this);
      }
    } else {
      return Handlebars.helpers["x"].apply(this, [expression, options]) ? options.fn(this) : options.inverse(this);
    }
  } catch (e) {
    if (!(/ReferenceError/.test(e))) {
      console.warn("{{#if " + expression + "}} hit an error:", e);
    }
  }
});

Handlebars.registerHelper("unless", function (expression, options) {
  try {
    if (expression.split(' ').length == 1 && (!/@(\w+)/.test(expression))) {
      if (options.data.root[expression] && !(options.data.root[expression])) {
        return (options.data.root[expression] !== 'true') ? options.fn(this) : options.inverse(this);
      } else {
        return options.fn(this);
      }
    } else {
      return (!Handlebars.helpers["x"].apply(this, [expression, options])) ? options.fn(this) : options.inverse(this);
    }
  } catch (e) {
    if (!(/ReferenceError/.test(e))) {
      console.warn("{{unless " + expression + "}} hit an error:", e);
    }
  }
});

Handlebars.registerHelper("x", function(expression, options) {
  var fn = function() {},
    decMatch,
    result;

  decMatch = /@(\w+)/g.test(expression);

  if (decMatch) {
    expression = expression.replace(/@(\w+)/g, '$1');
  }

  with (decMatch ? options.data : options.data.root) {
    try {
      result = eval(expression);
    } catch (e) {
      if (!(/ReferenceError/.test(e))) {
        console.warn("{{x " + expression + "}} hit an error:", e);
      }
    }
  }
  return result;
});