Synchronizing billing fields with the corresponding shipping fields
Since I don't know your markup, I don't know for sure if this will work, but it might

$("input[id*=Shipping]").change(function (event) {
  var billingId = this.id.replace('Shipping', 'Billing');
  $("#" + billingId).val($(this).val());
});


Basically, get every input with "Shipping" in its id, and when such an input changes, use its id to determine the corresponding billing-input.

Edit: While this solution is a neat little demonstration of the attribute-value-contains selector, it is - as the other answers have pointed out - better to use a class or data-attribute