JavaScript how to check drag direction
I am trying to monitor dragStart and dragEvent javascript, in order to conclude its direction, UP or DOWN.
H开发者_如何学运维owever i could not get any detail in arguments passed by the event -- that help to conclude.
Is there any better way to check drag direction , up or down?
Note: my problem is specifically happening at mojo javascript at webos
Thanks, -iwan
I didn't know about dragStart and dragEvent, but why not use onmousedown, onmousemove and onmouseup?
I made a modified version of http://dunnbypaul.net/js_mouse/. The direction is displayed in #status when you drag the image. Tested and works in IE5.5, IE6, IE7, IE8, Safari 5, Chrome 6 and Navigator 9. Works with Strict Doctype (probably other Doctypes also, didn't test them).
JavaScript:
var dragobj = null;
function getCurY(e) {
if (!e) e = window.event;
if (e.pageX || e.pageY)
return e.pageY;
else if (e.clientX || e.clientY)
return e.clientY + document.body.scrollTop;
}
function drag(context, e) {
dragobj = context;
document.onmousedown = function() { return false };
document.onmouseup = function() {
if (dragobj) dragobj = null;
document.getElementById('status').innerHTML = 'Direction: n/a';
}
var graby = getCurY(e);
var oriy = dragobj.offsetTop;
document.onmousemove = function(e) {
if (dragobj) {
dragobj.style.position = 'absolute';
var newy = oriy + getCurY(e) - graby;
var dir = newy > parseInt(dragobj.style.top, 10) ? 'down' : 'up';
dragobj.style.top = newy + 'px';
document.getElementById('status').innerHTML = 'Direction: ' + dir;
}
return false;
}
}
HTML:
<p onmousedown="drag(this, event)">
<img src="http://1.bp.blogspot.com/-u3FKHnFg8cA/Td56DmfliyI/AAAAAAAAAJ8/fTCFNCTs7iE/s1600/trollface%255B1%255D.jpg" alt="Trollface" />
</p>
<p id="status" style="position:absolute; top:0">Direction: n/a</p>
It won't tell you the direction, but you can get the position of the element you're dragging and figure out which direction it's going.
This might be helpful: http://dunnbypaul.net/js_mouse/.
You want to use dragOver. You could do something like this if you're only interested in vertical position:
Javascript:
<script type="text/javascript">
function getPosY(event) {
console.log(event.clientY);
}
</script>
HTML:
<body ondragover="getPosY(event)">
EDIT: Here's a jsfiddle. Make sure your js console is open.
You could have your function compare the clientY values to determine which direction the mouse is moving.
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