How to Move UI button or any element in x and y axis specifically after creation?

Button object as a location property that you can modify. Take a look at this snippet:

(function (thisObj) {
    buildUI(thisObj);
    function buildUI(thisObj) {
        var win = (thisObj instanceof Panel) ? thisObj : new Window("palette", "script", undefined, {
            resizeable: true
        });
        // Resize the pallete
        win.preferredSize = [400, 200];
        // Create a dummy button
        var btn = win.add("button", undefined, "OK");
        btn.onClick = function () {
            // Generate rnadom X and Y values
            var randomX = Math.random() * 400;
            var randomY = Math.random() * 200;
            // Change buttons position
            this.location = [randomX, randomY];
        }
        // Handle window resizing
        win.onResizing = win.onResize = function () {
            this.layout.resize();
        };
        // Show panel
        if (win instanceof Window) {
            win.center();
            win.show();
        } else {
            win.layout.layout(true);
            win.layout.resize();
        }
    }
})(this);