examples/handlebars/handlebars_helper_conditionals.js
Handlebars.registerHelper('iff', function(a, operator, b, opts) {
    var bool = false;
    switch(operator) {
       case '===':
           bool = a === b;
           break;
       case '>':
           bool = a > b;
           break;
       case '<':
           bool = a < b;
           break;
       default:
           throw "Unknown operator " + operator;
    }

    if (bool) {
        return opts.fn(this);
    } else {
        return opts.inverse(this);
    }
});