A method for jQuery Validation Plugin (http://jqueryvalidation.org/). It checks if a ZIP code entered contains one of a number of prefixes specified in an array. It can also check if a ZIP code is within a certain range or if it contains a specific format (e.g. USA, Canada, etc.). Client work.

zip-validation.js

/*
 Version:   	1.0
 File:          zip-validation.js
 Author:   	Juan Garcia
 Email:     	dev [at] soleilnoirmedia [dot] com
 Description: 	zipValidation.js contains a method for jQuery Validation Plugin (http://jqueryvalidation.org/).
 It checks if a ZIP code entered contains one of a number of prefixes specified in an array (A requirement from a client).
 It can also check if a ZIP code is within a certain range or if it contains a specific format (e.g. USA, Canada, etc.).
 Ideal to validate addresses for local deliveries.
 */

$.validator.addMethod("zipcode", function(value, element) {
	// Specify your array
	var prefixarray = ["10", "11", "12"];
	
	// Specify the size (from x index to y index of the string, exclusive ) of the "prefix" you want to validate against
	var prefix = value.slice(0, 2);
	
	// A single condition is checked (you can fix this by nesting, looping, chaining or other means), 
	// if you uncomment an "if" statement, comment out other "if" statements.
	// You can check for the "prefix" to exist in the specified array
	if ($.inArray(prefix, prefixarray) > -1) {
		return true;
	}
	
	/* Alternatively, you can specify a range, useful for US postal codes
	 * Eg. ^1[1-3]\d{3}$ Matches the range 10XXX to 15XXX (can be used with XXXXX-XXXX formated codes,
	 * where the last four numbers are irrelevant for validation purposes).
	 * Code:
	 * if (/^1[0-5]\d{3}/.test(value) ) {
	 *     return true
	 * }
	 */
	
	/* Alternatively, you can check only for a specific format.
	 * As it stands, it would check for valid US, Mexico formats: XXXXX-XXXX or XXXXX 
	 * or Canadian formats XXX-XXX or XXX XXX or XXXXXX (lower and upper case).
	 * Code:
	 * if ( /\d{5}-\d{4}$|^\d{5}$|^[a-zA-Z][0-9][a-zA-Z](-| )?[0-9][a-zA-Z][0-9]$/.test(value) ) {
	 *     return true
	 * }
	 *
	 */
	else {
		return false;
	}
},
// Depending on the type of validation you perform you can specify an error message.
"The ZIP code you entered is invalid / No delivery available to the specified ZIP code.");

// Usage example
$("form").validate({
	rules : {
		zip : {
			// This validation will be performed before our method; 
			// no need to go into our method if the ZIP code isn't even long enough to be valid.
			minlength : 5, 
			 // Our method.
			zipcode : "true"
		}
	},
	messages : {
		zip : {
			// Our method will provide its own error message.
			minlength : "The ZIP code you entered is too short." 
		}
	}
});