Guess my secret number from 0 - ?

Tasks
  1. When the user inputs a value that is outside of the range the program should display a different message with a quick hint
  2. When the user doesn't provide any input, the message should say so
  3. Move all javascript code into seperate .js files and include them in the html file
  4. Make a new input field in HTML, with a button next to it. When the user press this button, use the number to set a new maximum number