JavaScript How to Dynamically Move Div by Clicking and Dragging

Question

Okay it would seem like it should be simple. I need to take an already existing div and move it according to mouse position within the window. I have searched everywhere and

Answer 1

I just made a small change to the @adeneo very well working answer. If everything is enclosed in a function, and every event is attached to the div, you can use it as part of a library.

Call the following function passing an id. If the div does not exist it is created.

function drag_div(div_id){
var div;

div = document.getElementById(div_id);

if(div == null){
   div = document.createElement("div");
   div.id = div_id;
   div.style.position = "absolute";
   div.style.left = "0px";
   div.style.top = "0px";
   div.style.width = "100px";
   div.style.height = "100px";
   div.style.background = "red";
   div.style.color = "blue";
   document.body.appendChild(div);
}

div.addEventListener('mousedown', function(e) {
    div.isDown = true;
    div.offset = [
        div.offsetLeft - e.clientX,
        div.offsetTop - e.clientY
    ];
}, true);

div.addEventListener('mouseup', function() {
    div.isDown = false;
}, true);

div.addEventListener('mousemove', function(event) {
    event.preventDefault();
    if (div.isDown) {
        div.mousePosition = {

            x : event.clientX,
            y : event.clientY

        };
        div.style.left = (div.mousePosition.x + div.offset[0]) + 'px';
        div.style.top  = (div.mousePosition.y + div.offset[1]) + 'px';
    }
}, true);
}