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touchend event properties

Posted by: admin November 29, 2017 Leave a comment

Questions:

If I catch all touchend events from mobile devices with:

$(document.body).bind('touchend', function (e) {
var touch = e.touches[0]; // doesnt work
...

I need to get the touch.screenX, touch.screenY, touch.clientX and touch.clientX from the e paramter. All the examples I’ve seen suggest that e.touches will be a collection, and you can get at the touch details with e.touches[0]. In my tests on an ipad, e.touches is always undefined. I’m not using any jquery plugins.

Also tried e.targetTouches, which is also undefined.

Can anyone help?

Answers:

Actually, released touches will be found in the changedTouches array, ie:

e.changedTouches[0].pageX // get the end x page coordinate for a released touch

I think this is slightly more reliable than going through the originalEvent property.

You can read more on changedTouches here:
http://www.w3.org/TR/touch-events/#changedtouches-of-a-touchevent

Questions:
Answers:

The touches property is an TouchList object. You can see the TouchList class reference here.

If you monitor its length property with this example code on #log div:

$('#element').bind('touchstart', function(event) 
{
    $('#log').append(event.originalEvent.touches.length+'<br/>');
});

$('#element').bind('touchmove', function(event) 
{
    $('#log').append(event.originalEvent.touches.length+'<br/>');
});

$('#element').bind('touchend', function(event) 
{
    $('#log').append(event.originalEvent.touches.length+'<br/>');
});

you will obtain 1 while executing touchstart and touchmove, an 0 when executing touchend. That is why you obtain undefined from e.touches[0].