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.

For firefox links appear to be "special". The only way I was able to get this working was to use the createEvent described here on MDN and call the initMouseEvent function. Even that didn't work completely, I had to manually tell the browser to open a link...

var theEvent = document.createEvent("MouseEvent");
theEvent.initMouseEvent("click", true, true, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
var element = document.getElementById('link');
element.dispatchEvent(theEvent);

while (element)
{
    if (element.tagName == "A" && element.href != "")
    {
        if (element.target == "_blank") { window.open(element.href, element.target); }
        else { document.location = element.href; }
        element = null;
    }
    else
    {
        element = element.parentElement;
    }
}