javascript - "document.getElementByClass is not a function"

I am trying to run a function onclick of any button with class="stopMusic". I'm getting an error in Firebug

document.getElementByClass is not a function

Here is my code:

var stopMusicExt = document.getElementByClass("stopButton");
    stopButton.onclick = function() {

        var ta = document.getElementByClass("stopButton");
        document['player'].stopMusicExt(ta.value);
        ta.value = "";
    };

Answer

You probably meant document.getElementsByClassName() (and then grabbing the first item off the resulting node list):

var stopMusicExt = document.getElementsByClassName("stopButton")[0];


stopButton.onclick = function() {
    var ta = document.getElementsByClassName("stopButton")[0];
    document['player'].stopMusicExt(ta.value);
    ta.value = "";
};

You may still get the error

document.getElementsByClassName is not a function

in older browsers, though, in which case you can provide a fallback implementation if you need to support those older browsers.