Capture keypress in Javascript (Google Docs)

问题

I'm trying to write a little greasemonkey script/bookmarklet/what have you for Google Docs. The functionality I'd like to add needs a keypress/keyup/keydown event handler (one of those three). Unfortunately, Javascript isn't my forté, and I can't seem to capture (?) a keypress event to while in the edit pane. As a last resort, I've tried the following:

javascript:(function(){
  els = document.getElementsByTagName("*");
  for(i=0;i<els.length;i++){
    els[i].onkeypress=function(){alert("hello!");};
    els[i].onkeyup=function(){alert("hello2!");};
    els[i].onkeydown=function(){alert("hello3!");};
  }
})();

However, this still doesn't capture keypresses in the editing pane - no annoying alerts (although it seems to work for most other sites...). I've checked in Chrome and Firefox both (I can't get it to work in either one).

I tried "Log Events" in Firebug (and checked out all the registered events via a neat little extension to Firebug, Eventbug); it didn't seem like those events were firing on keypresses.

Edit:
To clarify [Tim], I made this screenshot with some annotations...

The "editing pane" I'm talking about seems to be a bunch of Javascripted-up divs displaying what I type.

Any ideas? Thanks!

回答1:

Editing in Google Docs uses an iframe. You need to attach a listener to the iframe's document. It seems to do something complicated with the iframe I haven't yet been able to work out fully, but the following seems to work for Firefox:

var iframe = document.getElementsByTagName("iframe")[0];
if (iframe) {
    iframe.contentDocument.addEventListener("keypress", function(evt) {
        console.log("iframe keypress: " + evt.which);
    }, false);
}

回答2:

Seems to work for me... but I'm using jQuery $(document).ready() to make sure my page is loaded before attaching any event. I think you could do it in bare javascript with :

window.onload = function()
{
  els = document.getElementsByTagName("*");
  for(i=0;i<els.length;i++) {
    els[i].onkeypress=function(){alert("hello!");};
  }
}

By the way you can't attach more than one function to the event:

for(i=0;i<els.length;i++){
    els[i].onkeypress=function(){alert("hello!");};
    els[i].onkeypress=function(){alert("hello2!");};
    els[i].onkeypress=function(){alert("hello3!");};
}

The element will register only the last one (it overrides the previous function), in this case "alert("hello3!");"

回答3:

You do not need to attach the listener to all the elements on the page. To attach it to the document is enough.

window.addEventListener('load', function() {
    document.addEventListener('keypress', function() { alert("hello!"); });
}

Since it is a GreaseMonkey script you do not need to worry about IE and can use the addEventListener method.

来源：https://stackoverflow.com/questions/4373666/capture-keypress-in-javascript-google-docs

标签

javascript

greasemonkey

google-docs

bookmarklet