You must first develop an Ext JS application with Sencha Cmd and then package it with compile electron to exe in order to make it executable. The fundamentals for packaging an HTML5 desktop application follow very similar guidelines as those for packaging an HTML5 mobile app using Apache Cordova or Adobe Phone Gap. Visit the website.
https://www.sencha.com/blog/creating-installable-desktop-applications-with-ext-js-and-electron/