Remove all the children DOM elements in div

First of all you need to create a surface once and keep it somewhere handy. Example:

var surface = dojox.gfx.createSurface(domNode, widthInPx, heightInPx);

domNode is usually an unadorned <div>, which is used as a placeholder for a surface.

You can clear everything on the surface in one go (all existing shape objects will be invalidated, don't use them after that):

surface.clear();

All surface-related functions and methods can be found in the official documentation on dojox.gfx.Surface. Examples of use can be found in dojox/gfx/tests/.

node.innerHTML = "";

Non-standard, but fast and well supported.

while (node.hasChildNodes()) {
    node.removeChild(node.lastChild);
}