mouse up on lines

HTML

<script src="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraph,css"></script>
<script src="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraphcore.js"></script>
<div id="box"></div>

CSS

#box {
    width:500px;
    height:500px;
}

JavaScript

var board = JXG.JSXGraph.initBoard('box', {
        boundingbox: [-4,4,4,-4], 
        keepaspectratio: true, 
    });

var p = board.create('point',[0,0],{size:16});
var q = board.create('point',[1,3],{size:16});
var l = board.create('line', [p, q]);

l.on('touchend', function () {
    alert('up!');
});