request.js

Request = {
    send: function (options) {
        this.options.success = this.success.bind(this);
        this.options.error = this.error.bind(this);
        this.options = _.extend(this.options, options)
        return this.request(this.options);
    },
    request: function (options){
        return new Promise(function (resolve, reject){
            // Do the usual XHR stuff
            var req = new XMLHttpRequest();
            req.open(options.method, options.url);

            req.onload = function() {
                // This is called even on 404 etc
                // so check the status
                if (req.status == 200) {
                    // Resolve the promise with the response text
                    resolve(req.response);
                }
                else {
                    // Otherwise reject with the status text
                    // which will hopefully be a meaningful error
                    reject(Error(req.statusText));
                }
            };

            // Handle network errors
            req.onerror = function() {
                reject(Error("Network Error"));
            };

            // Make the request
            req.send();
        });
    }
}

somefile.js

  save: function (e) {
        var modal,
            template,
            form;
        this.disable_save();

        this.form = $(this.form_el);


        this.beforeSave()
            .then(this.send.bind(this))
            .then(this.success.bind(this))
            .then(this.afterSave.bind(this))
            .catch(Alert.error.bind(Alert))
            .then(this.enable_save.bind(this))
    },
    send: function (data) {
        data = this.form.serialize();
        return
            Request.send({
                url: this.save_url,
                type: 'POST',
                data: data
            });
    },