JS autoclick button after 4 sec. (Greasemonkey)

Hello how to make a开发者_如何学运维 simple code in JS to Greasemonkey which click button on page after 4 sec? I'm fully beginner in JS.

Here is code of this button ;):

<a class="doIt" href="#" onClick="func_x()"></a>

Thanks for help.

setTimeout(function() {
    unsafeWindow.func_x(); // onclick event function
}, 4000);

or better yet

setTimeout(function() {
    location.assign("javascript:func_x()"); // onclick event function
}, 4000);

setTimeout(function() {
    var evt = document.createEvent("MouseEvents");
    evt.initMouseEvent("click", true, true, window,
                       0, 0, 0, 0, 0,
                       false, false, false, false,
                       0, null);
    var link = document.querySelector("a.doIt");
    link.dispatchEvent(evt);
}, 4000);

References:

• https://developer.mozilla.org/en/DOM/document.createEvent
• https://developer.mozilla.org/en/DOM/event.initMouseEvent
• https://developer.mozilla.org/En/DOM/Document.querySelector
• https://developer.mozilla.org/en/DOM/element.dispatchEvent

Live example:

• https://developer.mozilla.org/samples/domref/dispatchEvent.html