src/router-view.js
// animate the next view at the same time the current view is removed
animate the next view at the same time the current view is removed
animate the next view at the same time the current view is removed
with(viewSlot, previousView, callback) {
    let promise = Promise.resolve(callback());
    if (previousView !== undefined) {
      return Promise.all([viewSlot.remove(previousView, true), promise]);
    }
    return promise;
  }
with ( viewSlot , previousView , callback ) { let promise = Promise . resolve ( callback ( ) ) ; if ( previousView !== undefined ) { return Promise . all ( [ viewSlot . remove ( previousView , true ) , promise ] ) ; } return promise ; }
animate the next view at the same time the current view is removed
animate the next view at the same time the current view is removed