Validate A Text Field For Multiple Criteria?

I have a text field where a user can enter either a(n):American zip code (example: "02475")Canadian zip code (example: "A3F 4G6")A "city/state abbreviation" combination (example: "Toronto, ON", or "Las Vegas, NV")For the most part, users don't have much of a problem with the first two criteria, but some people have some trouble with the third, either by entering simply a state ("NB", or "Texas"), a city, or spelling out the state name "Chicago, Illinois". I need to put together some validation that makes sure that:

If the entered text is not an american or canadian zip code (IOW, if the entered text contains no numbers at all - in that case, move on to the next validation check)Check to see if the third to last character is non alphanumeric (if they entered the city/state combination correctly, there would be some sort of non-alphanumeric separator between the city and state abbreviation)if the entered text doesn't fit the criteria, return the error.

function hasNumbers(string) {
var regex = /d/g;
return regex.test(string);
}

[code]....