title: Javascript input mask that enforces sections?
body: <p>I figure, given a week and Red Bull, I could make something that does this, but first, I wanted to find out if it had been done already. </p>
  
  <p>I know input masks already exist: For example, <code>__/__/____</code>. So you can just type a date, and voila, <code>12/31/2010</code>. </p>
  
  <p>However, if I were to go in and realize I meant to put December 20th, I go to the 3 in 31, hit delete once, and now it displays <code>12/12/010_</code>. That's not very helpful. It's because the internal value is still simply "12312010", so when you delete '3' it becomes "1212010", and that is inserted into the mask accordingly.</p>
  
  <p>Is there any existing JavaScript mask that will enforce blocks? So that, if I did what I described above, it would then display <code>12/1_/2010</code>? I don't mind if it still submits as "1212010", as long as it displays properly. </p>
  
  <p>Would prefer a jQuery plugin, but straight JavaScript works.</p>