How can I use an AngularJS filter to format a number to have leading zeros?

Question

I checked the documentation. What I would like is for my numbers to have four digits and leading zeros.

22 to 0022
1  to 0001

Can someone

Answer 1

Another example:

// Formats a number to be at least minNumberOfDigits by adding leading zeros
app.filter('LeadingZerosFilter', function() {
  return function(input, minNumberOfDigits) {
    minNumberOfDigits = minNumberOfDigits || 2;
    input = input + '';
    var zeros = new Array(minNumberOfDigits - input.length + 1).join('0');
    return zeros + input;
  };
});