Mouse drag effect code based on jquery_jquery

I remember that in a previous essay on "Drag Layer", I implemented dragging by using a Boolean variable to determine whether an element could be dragged.
After reading some things in the past two days, I found that there is no need to set this Boolean variable;

Implementation process:
When the mouse is pressed, give the document object (of course it can also be other DOM objects) Bind a handler function to the movement event, and also bind a release handler function to when the mouse is raised.

Copy code The code is as follows:

//When the mouse is pressed and moved (drag) , the function called;
function startSelection(event){
...
}

//The processing function when canceling the move;
function cancelSelection() {
$ (document).unbind('mousemove', startSelection).unbind('mouseup', cancelSelection);
　}
//The function called when the mouse is pressed
function imgMouseDown(event){
$(document).mousemove(startSelection).mouseup(cancelSelection);
}
$img.bind("mousedown",imgMouseDown)