Don’t write js output when in extract mode.

When I change a scss file in extract mode, it seems the bundle for js is being written again with the same exact content as before which is not needed. All I expect is for the output css to change, not the js as well. This is a problem for watchers, it will trigger a change regardless of content, I think it takes last modified timestamp. This causes the browser to reload, but I just want the css to be updated inline. Is there a workaround or a fix available? Thanks.