How is document.createEvent supposed to work with key events?

Question

I am trying to simulate keypresses in a web application, it is for an embedded system but it uses a Webkit derived browser. I have tested the code in Chrome and get the same error.

I tried to use code snippets from this example from Yahoo, but I keep getting the same error when firing the event using dispatchEvent. "target" is an HTML element in the DOM tree.

function fireEvent(target) {
    var evt = document.createEvent("UIEvent");
    evt.initEvent("keypress", true, true);
    target.dispatchEvent(evt);
}

It always throws:

"Error: UNSPECIFIED_EVENT_TYPE_ERR: DOM Events Exception 0"

I have tried createEvent("Events") as well and it always boils down to the same exception, both on the embedded system and in Chrome.

Solution 1

Ok, when doing further testing, it seemed that when all key event parameters was properly initialised, then dispatchEvent worked without fireing an exception.

The following code works.

function fireEvent(target) {
    var evt = document.createEvent("Events");
    evt.initEvent("keypress", true, true);

    evt.view = window;
    evt.altKey = false;
    evt.ctrlKey = false;
    evt.shiftKey = false;
    evt.metaKey = false;
    evt.keyCode = 0;
    evt.charCode = 'a';

    target.dispatchEvent(evt);
}

Solution 2

Keypress is an UIEvent. You should use initUIEvent( 'type', bubbles, cancelable, windowObject, detail ) rather than initEvent(). But for firefox, which implements a keyEvents, you should create a KeyEvents and initKeyEvents().