How do I programmatically click on an element in JavaScript?

The document.createEvent documentation says that “The createEvent method is deprecated. Use event constructors instead.“

So you should use this method instead:

var clickEvent = new MouseEvent("click", {
    "view": window,
    "bubbles": true,
    "cancelable": false
});

and fire it on an element like this:

element.dispatchEvent(clickEvent);

as shown here.