title: jquery check if string starts with 1234
body: <p>Thanks for taking the time to answer my question.</p>
  
  <p>I want to check if a string has exactly 7 characters and starts with "1234". How do I do that?</p>
  
  <p>I know of string.substring but am not sure if I shouold use regex or are there any other alternative. Thanks in advance!</p>