Need help making a code for this task, with no json, jquarry and so on..

Create an address book application using JavaScript (plus HTML and CSS). (Use plain JavaScript, no third party libraries!)

The required functionality is the following:

• Entries
  • Entries have the following fields: name, telephone number, email
  • Individual entries must be represented as an Entry object
  • The contact list must be represented as an array of Entry objects
  • The application must be shipped with some sample initial data (meaning, with a non-empty address book)
• Display a list of entries
  • Emails should be clickable links that open in the mail client
• Add a search field to filter the list
  • Only those entries are displayed that contain the searched string as part of the name, telephone, or email
  • Matching is case-insensitive
• The user can delete existing entries
  • Ask for a confirmation before deleting the entry
• The user can add new entries
  • Perform input check
    • The name field must never be empty
    • Either tel or email has to be filled in
    • Email has to be a valid email
    • Tel may contain only numbers and + - ( ) and space