I have tried to upgrade a SPFx project from Yeoman 1.3.4 to 1.4.0 as a result of this React is upgraded from version 14 to version 15.6. As a result my code has gone from working to not working :- private _showAlert(): void { const alert: React.ReactElement = React.createElement( Alert, { message: strings.CustomSearchPlaceholderModeOnAlert } );Read more