6.Difference b/w Constructor vs ngoninit?

We mostly use ngOnInit in every startup/announcement and avoid things to work in builders. The constructor should only be used to start class members but should not do the actual “work”.
So you should use the constructor() to set Dependency Injection and not much. ngOnInit() is a better “starting point” – this is where / when component combinations are solved.
We use constructor() for all the initialization/declaration.
It’s better to avoid writing actual work in the constructor.
The constructor() should only be used to initialize class members but shouldn’t do actual “work”.
So we should use constructor() to set up Dependency Injection, Initialization of class fields, etc.
ngOnInit() is a better place to write “actual work code” that we need to execute as soon as the class is instantiated.
Like loading data from Database — to show the user in your HTML template view. Such code should be written in ngOnInit().