Modifying an SVG animateTransform at end-of-repeat-loop

Question

I'm trying to make an object rotate faster and faster as time goes on, and I'm having trouble having an event fire every time the animation repeats itself. SVG/SMIL's repeatEvent seems to be what I need, but in the following code, onSpinEnd() doesn't appear to be called at all. What am I doing wrong?

    <path id='coloredPart' d='…'>
        <animateTransform
            id='spin'
            attributeName='transform'
            begin='0s'
            dur='5s'
            type='rotate'
            from='0 0 0'
            to='-360 0 0'
            repeatCount='indefinite'
        />
    </path>

    <script>  <![CDATA[
        var spin = document.getElementById('spin');
        var onSpinEnd = function() {
            var intPart = 0;
            intPart = parseInt(spin.getAttribute('dur')[0].slice(0, -1));
            console.log(intPart);
            if (intPart > 1) --intPart;
            spin.setAttribute('dur', intPart.toString() + 's');
        };
        spin.addEventListener('repeatEvent', onSpinEnd, false)
        ]]>   
    </script>

As it turns out, [0].slice(0, -1)) won't give me "16" from "16s"; .slice(0, -1)) will. That line should read:

intPart = parseInt(spin.getAttribute('dur').slice(0, -1));

Answer 1

I'm not sure what the slice is for. This seems to work on Firefox.

var onSpinEnd = function() {
    var spin = document.getElementById('spin');
    var intPart = 0;
    intPart = parseInt(spin.getAttribute('dur')[0]);
    console.log(intPart);
    if (intPart > 1) --intPart;
    spin.setAttribute('dur', intPart.toString() + 's');
};

Additionally, as far as I know only Opera and Firefox currently fire SMIL events.