getElementTransitionDuration.js

function getElementTransitionDuration(elem, property) {
        // this currently only supports Webkit browsers, but should be easy enough to apply to others as they begin to support CSS transitions
	var td = elem ? window.getComputedStyle(elem)['-webkit-transition-duration'].split(', ') : [],
		tp = elem ? window.getComputedStyle(elem)['-webkit-transition-property'].split(', ') : [],
		durations = {},
		longest = 0,
		i = td.length;
	while( --i ) {
		var dur = parseFloat(td[i], 10);
		if(i < tp.length) {
			durations[tp[i]] = dur;
		}
		longest = dur > longest ? dur : longest;
	}
	if(!property) {
		return longest;
	} else if(durations[property]) {
		return durations[property];
	} else {
		return 0;
	}
}