Example of a SugarCRM sidecar Plugin that "mixes in" a keydown event listener for all postal code fields and makes a call to an Sugar REST endpoint to retrieve City name

PostalCodeValidator.js

(function (app) {
    app.events.on("app:init", function () {
        /**
         * This plugin allows views that contain *_postalcode attributes
         * to be wired up with a keypress event that will contact a postal-code validator
         * service
         *
         * <pre><code>
         *  {
         *     //Sample component
         *     plugins: ['PostalCodeValidator'],
         *
         *  }
         * </code></pre>
         */
        app.plugins.register('PostalCodeValidator', 'view', {

            /**
             * Locate all *_postalcode fields and attach a keydown event handler
             */
            onAttach: function () {
                app.logger.info('PostalCodeValidator: Inside the onAttach method');
                this.events = (this.events) ? this.events : {};
                _.extend(this.events, {
                    "keydown input[name*='_postalcode']" : _.bind(function (e) {
                        if (!this.disposed) {
                            //Trigger call to api when the "Enter"
                            //key has been entered
                            if (e.key === 'Enter') {
                                var currentPostalCode = this.$el.find("input[name='" + e.target.name + "']").val();
                                app.logger.info('Calling API with the value: ' + currentPostalCode);
                                var restURL = app.api.buildURL('CityValidator') + '/' + currentPostalCode + '/' +
                                    e.target.name;
                                app.logger.info(restURL);
                                app.api.call('read', restURL, {}, {
                                    success: _.bind(this._handleSuccess, this),
                                    error : _.bind(this._handleError, this)
                                });
                            } else {
                                app.logger.info('The key typed in is: ' + e.key);
                            }
                        }

                    }, this)
                });

            },

            _handleSuccess : function (data) {

                if (this.disposed) {
                    return;
                }

                //use the postcode_attr prop to determine the City attribute
                var postCodeAttr = data.postcode_attr;
                //the assumption is that all postcode fields end with "_postalcode" in the name
                //Let's strip this off and use what's left to infer the City
                var postalCodeIndex = postCodeAttr.indexOf('_postalcode');
                if (postalCodeIndex > 0) {
                    //save the substring from 0 to postalCodeIndex + 1 (Why postalCodeIndex + 1? To keep the underscore
                    //in the resulting substring)
                    var baseAttr = postCodeAttr.substr(0, postalCodeIndex + 1);
                    //let's add city to the end of the base attribute
                    var cityAttr = baseAttr + 'city';
                    //Does this exist on our Model? If so, then set it. If not, then do nothing or maybe throw an Alert?.
                    if (_.has(this.model.fields, cityAttr)) {
                        this.model.set(cityAttr, data.city);
                    }
                }
            },

            _handleError : function (data) {
                app.logger.info('Data param is: ' + data);
                if (this.disposed) {
                    return;
                }

                app.logger.info('Leaving the error handler');
            }
        });
    });
})(SUGAR.App);

record.js

// noinspection BadExpressionStatementJS
({
    extendsFrom: 'AccountsRecordView',

    /**
     * @inheritDoc
     */
    initialize: function (options) {
        SUGAR.App.logger.info('Inside the initialize method of my custom AccountsRecordView controller');
        
        //Add the postcode validator plugin to the list of existing plugins
        this.plugins = _.union(this.plugins || [], ['PostalCodeValidator']);
        
        SUGAR.App.logger.info('Custom View After the addition of PostalCodeValidator');
        
        this._super('initialize', [options]);
        
        SUGAR.App.logger.info('Custom Accounts View, after call to the parent initialize method');      
    },
})