title: Add leading zeroes to a string
body: <p>I want to add some leading zeroes to a string, the total length must be eight characters. For example:</p>
  
  <p>123 should be 00000123<br>
  1243 should be 00001234<br>
  123456 should be 00123456<br>
  12345678 should be 12345678</p>
  
  <p>What's the easiest way?</p>