Answers for "has no initializer and is not definitely assigned in the constructor."

Property 'firstName' has no initializer and is not definitely assigned in the constructor

"angularCompilerOptions": {
    //   ...
    "strictPropertyInitialization": false
    //   ...
  }

Property 'products' has no initializer and is not definitely assigned in the constructor.

//inside tsconfig.json file
"angularCompilerOptions": {
    //   ...
    "strictPropertyInitialization": false
    //   ...
  }

Property '...' has no initializer and is not definitely assigned in the constructor

Just go to tsconfig.json and set

"strictPropertyInitialization": false
to get rid of the compilation error.

Otherwise you need to initialize all your variables which is a little bit annoying