title: Angular 4 form validation and Error Message
body: <p>I have to implement validation for forms in my application. I am using angular 4. I have 10 more forms in my application. I don't know if my question is valid or not. I am really confused with this implementation.</p>
  
  <p>My question:
  I need to add validation in form fields including mandatory and validation like email, phone number etc, If the user enter the form user knows some fields user may don't know what need to fill in other fields. But need to save valid fields and need to show the error message in form.</p>
  
  <p>How can i implement in front end i am using Angular 4 and back end with nodejs</p>