title: regex to find number of specific length, but with any character except a number before or after it
body: <p>I'm trying to work out a regex pattern to search a string for a 12 digit number. The number could have any number of other characters (but not numbers) in front or behind the one I am looking for.</p>
  
  <p>So far I have <code>/([0-9]{12})/</code> which finds 12 digit numbers correctly, however it also will match on a 13 digit number in the string.</p>
  
  <p>the pattern should match <code>123456789012</code> on the following strings</p>
  
  <ul>
  <li>"rgergiu123456789012ergewrg"</li>
  <li>"123456789012"</li>
  <li>"#123456789012"</li>
  <li>"ergerg ergerwg erwgewrg \n rgergewrgrewg regewrge 123456789012 ergwerg"</li>
  </ul>
  
  <p>it should match nothing on these strings:</p>
  
  <ul>
  <li>"123456789012000"</li>
  <li>"egjkrgkergr 123123456789012"</li>
  </ul>