The older approach to creating events uses APIs inspired by JAVA

custom_js_event.js

// create event
var evt = document.createEvent("Event");

// initializing the event
evt.initEvent("anyName", true, true);

// add event handler
document.addEventListener("anyName", function(e){
  // your handler logic
  console.log("e.target: ", e.target);
}, false);

// dispatch the event
document.dispatchEvent(evt);