How to use the scratch-gui.initFullScreen function in scratch-gui

const initGuiState = guiInitialState => {
    const pathname = window.location.pathname.toLowerCase();
    const parts = pathname.split('/').filter(Boolean);
    // parts[0]: 'preview'
    // parts[1]: either :id or 'editor'
    // parts[2]: undefined if no :id, otherwise either 'editor' or 'fullscreen'
    if (parts.indexOf('editor') === -1) {
        guiInitialState = GUI.initPlayer(guiInitialState);
    }
    if (parts.indexOf('fullscreen') !== -1) {
        guiInitialState = GUI.initFullScreen(guiInitialState);
    }
    return guiInitialState;
};

module.exports.initGuiState = guiInitialState => {
    const pathname = window.location.pathname.toLowerCase();
    const parts = pathname.split('/').filter(Boolean);
    // parts[0]: 'projects'
    // parts[1]: either :id or 'editor'
    // parts[2]: undefined if no :id, otherwise either 'editor' or 'fullscreen'
    if (parts.indexOf('editor') === -1) {
        guiInitialState = GUI.initPlayer(guiInitialState);
    }
    if (parts.indexOf('fullscreen') !== -1) {
        guiInitialState = GUI.initFullScreen(guiInitialState);
    }
    return guiInitialState;
};