Problem
$ ng serve --open
Versions of @angular/compiler-cli and typescript could not be determined.
The most common reason for this is a broken npm install.
Please make sure your package.json contains both @angular/compiler-cli and types cript in
devDependencies, then delete node_modules and package-lock.json (if you have one ) and
run npm install again.
Solve
npm install --save @angular/compiler-cli
