Angular CLI Error: The serve command requires to be run in an Angular project, but a project definition could not be found

I was also getting this issue and solved by running below command.

ng update @angular/cli --migrate-only --from=<WhateverVersionYouAreCurrentlyOn>

e.g.

ng update @angular/cli --migrate-only --from=1.7.3

getting ref from here

angular angular5 angular-cli

make sure that you are running the command in the application root folder..

angular angular5 angular-cli

if you have downloaded a project,do in the project

npm install

CodeHunter