handler file with ajax functionality added in

handler.js

(function(window) {
    
    window.renderTemplate = function() {

        var template, context;
        // Handle ajax requests
        var ajax = function() {
            // Create normalized xhr object
            function xhr() {
                // To stifile any exceptions
                try {
                    // Detect native XMLHttpRequest object
                    if('XMLHttpRequest' in window && window.XMLHttpRequest) {
                        return new window.XMLHttpRequest();
                    }
                    // Detect IE ActiveX object
                    if('ActiveXObject' in window && window.ActiveXObject) {
                        return new window.ActiveXObject("Microsoft.XMLHTTP");
                    }
                }
                // Swallow exceptions and return undefined
                catch(e) {}
            }

            // Cache to only create xhr function once
            return function(path, callback) {
                // Create new XHR instance
                var _xhr = xhr();
                // Ensure XHR object exists
                if(xhr) {
                    // Connect to server
                    _xhr.open("GET", path, true);
                    // Handle readyState and fresh / cached results
                    _xhr.onreadystatechange = function() {
                        if(_xhr.readyState === 4 && 
                            _xhr.status === 200 || _xhr.status === 304) {
                            // Trigger the callback with the XHR object
                            callback(_xhr);
                        }
                    };
                    // Initialize the request
                    _xhr.send(null);
                }
            };
        }();

        // Container node to render template into and paths to template and context
        return function(node, paths) {
            // Fetch template markup
            ajax(paths.template, function(xhr) {
                template = xhr.responseText;
                // Fetch the context object and parse into an Object
                ajax(paths.context, function(xhr) {
                    context = JSON.parse(xhr.responseText);
                    // Template and handler have been set safe to render
                    template && context && render();
                });
            });
        };        

        // Render block

    }();

})(this);