Type error: Property ‘onRouteChangeStart’ does not exist on type ‘SingletonRouter’.

// だめ
Router.onRouteChangeStart = url => {};

// ok
Router.events.on('routeChangeStart', (url) => {
    console.log(url);
    NProgress.start();
})

// だめ

Router.onRouteChangeStart = url => {};

// ok

Router.events.on('routeChangeStart', (url) => {

console.log(url);

NProgress.start();

})

参考記事