Mouseup not working after mousemove on img

问题

I'm trying to do a simple drag script. The idea is to save the position when the mouse is down, update the view while the mouse is moving, and stop when mouse is up. Problem, mouseup event isn't working properly.

See the code:

var target = $('a')
var pos = 0;
var dragging = false;

$(document).mousedown(function(e) { pos=e.pageX; dragging = true })
$(document).mouseup(function() { dragging = false })
$(document).mousemove(function(e) {
    if(dragging){ 
        target.css('left', e.pageX-pos);
    }
})  ​

Why mouseup works with a "a" tag: http://jsfiddle.net/leyou/c3TrG/1/

And why mouseup doesn't work with a "img" tag: http://jsfiddle.net/leyou/eNwzv/

Just try to drag them horizontally.

Same probleme on ie9, ff and chrome. Windows7

回答1:

Just add e.preventDefault() to your mousedown handler, like this:

var target = $('img')
var pos = 0;
var dragging = false;

$(document).mousedown(function(e) { e.preventDefault(); pos=e.pageX; dragging = true })
$(document).mouseup(function() { dragging = false })
$(document).mousemove(function(e) {
    if(dragging){ 
        target.css('left', e.pageX-pos);
    }
})

See working demo .

The rationale is the browser was also doing his own native image drag and drop (like to drag an image and drop it in an application outside the browser) so you need to cancel that default drag and drop with .preventDefault() .

来源：https://stackoverflow.com/questions/13236484/mouseup-not-working-after-mousemove-on-img