Angular CLI - Typescript throws: Cannot read property 'length' of undefined

Question

I run in angular 4 project with ng serve and i get error

Cannot read property \'length\' of undefined

but I don\'t have any property length in

Answer 1

Most likely you have changed around your modules in a way that needs the CLI to be restarted.

I had the same error running ng serve after removing a component from a module. By restarting that process and re running ng serve the error went away.