Question

I’m trying to make a div that expands left, right, up, and down depending on where the mouse is. But when I move the mouse, the div just pops up and doesn’t do anything. What is wrong in what I’m doing?

(function() {
    document.onmousemove = function(e) {
        draw(e);
    };

    function draw(e) {
        var method = [
            e.pageX ? e.pageX : e.clientX,
            e.pageY ? e.pageY : e.clientY
        ];
        var X = method[0],
            Y = method[1];
        var html = '<div class="box" style="padding-top:' + Y + ';padding-bottom:' + Y + ';padding-left:' + X + ';padding-right:' + X + '"></div>'
            ;
        document.body.innerHTML = html;
    }
})();​

Answer 1

You forgot the unit px:

(function() {
    document.onmousemove = function(e) {
        draw(e);
    };

    function draw(e) {
        var method = [
            e.pageX ? e.pageX : e.clientX,
            e.pageY ? e.pageY : e.clientY
        ];
        var X = method[0],
            Y = method[1];
        var html = '<div class="box" style="background-color:red;padding-top:' + Y + 'px;padding-bottom:' + Y + 'px;padding-left:' + X + 'px;padding-right:' + X + 'px"></div>'
            ;
        document.body.innerHTML = html;
    }
})();​

(I’ve also added a red background in order to make the DIV visible)

jsFiddle: http://jsfiddle.net/8LUwp/