An unhandled exception occurred: Cannot find module 'domelementtype' Require stack

 An unhandled exception occurred: Cannot find module 'domelementtype'

[ng] Require stack:

Solution

Step 1: Delete node_modules folder

Step 2 : npm install 

Step 3 : start server

Step 4 : enjoy

What is the difference between constructor and ngOnInit? | Demo | Example

Demo URL

Constructor	ngOninit
A constructor is not the concept of Angular. It is the concept of JavaScript's class.	ngOninit is the second stage of Angular component lifecycle hook whenever is called when angular is done which creating the component.
Constructor is best place to add all dependencies	ngOninit function which guarantees you that the component has already been created.
Constructor is automatically called at the time of creating the object of the class.	Invoked by Angular when component is initialized
Used for Injecting dependencies	Actual business logic performed
we should use constructor() to setup Dependency Injection	is a better place to write "actual work code" that we need to execute as soon as the class is instantiated.

What is the difference between Components and Directives?

Demo URL

@Components	@Directives
For register component we use @Component meta-data annotation.	For register directives we use @Directive meta-data annotation.
Component is a directive which use shadow DOM to create encapsulate visual behavior called components. Components are typically used to create Ul widgets.	Directives are used to add behavior to an existing DOM element.
Component is used to break up the application into smaller components.	Directive is used to design reusable components.
Only one component can be present per DOM element.	Many directive can be used in a per DOM element
Component is used to define pipes	You can't define Pipes in a directive.
@View decorator or templateurl template are mandatory in the component.	Directives don't have a View.