JSFiddle - React, Tailwind, and code Playground

HTML

<button>Button</button>

JavaScript

//creating new event
var event = new Event("customAction");

//assigning the event handler to a object
document.querySelector("button").addEventListener("customAction", function() {
    setTimeout(function() {
    	document.querySelector("button").innerHTML = "Event Triggered";
    }, 3000);
}, false);

//calling the event handler manually
document.querySelector("button").dispatchEvent(event);