Require to load CSS requires a css.js plug-in, you can refer to Use RequireJS to unified manage JS and CSS

Can requirejs reference CSS? Or is the CSS all written in JS?

Failed to load resource: the server responded with a status of 404 (Not Found)
Your "XXCSS.js" file cannot be found at all. Check to see if there is anything wrong? Is the path correct?

The css referenced by require must be a dependency of a certain js, and it must be declared as css in the header

datepicker: {
    deps: [
        'jquery',
        'css!../../jslibs/jquery-ui/themes/base/jquery-ui.css',
        'css!../../jslibs/jquery-ui/themes/base/datepicker.css',
        'css!../../jslibs/jquery-ui/themes/base/base.css',
    ]
}