Ionic Serve throws a Type-Error: Appscripts.serve

Execute this command:

npm install --save-dev @ionic/app-scripts@latest

After that your app should work using

ionic serve

This is the same as mine when trying serve old project in updating Ionic3, all gonna error something like that, but when start a new project again its gonna work well

Running this command works for me

npm install --save-dev @ionic/app-scripts@latest

and then

ionic serve