world email and domain validation in javascript

email_domain_validation.js

var email_validate = function(s) {

	if (typeof(s) !== 'string') {
		return false;
	}

	var parts = s.split('@');

	if (parts.length !== 2) {
		// should be [email protected]
		return false;
	}

	var local_part = parts[0];

	if (local_part.length > 64) {
		// local_part is too long
		return false;
	}

	if (local_part[0] === '.' || local_part[local_part.length - 1] === '.') {
		// . must not be the first or last character
		return false;
	}

	var lp_m = local_part.match(/[\p{L}\p{N}\.!#\$%&'\\\*\+-/=\?\^_`\{\|\}~]/gu);
	if (lp_m === null) {
		// all invalid characters
		return false;
	} else if (lp_m.length !== local_part.length) {
		// invalid character in local part
		return false;
	}

	if (domain_validate(parts[1]) === false) {
		// domain failed validation
		return false;
	}

	return true;

}

var domain_validate = function(s) {

	if (typeof(s) !== 'string') {
		return false;
	}

	/*
	The labels must follow the rules for ARPANET host names.  They must
	start with a letter, end with a letter or digit, and have as interior
	characters only letters, digits, and hyphen.  There are also some
	restrictions on the length.  Labels must be 63 characters or less.
	*/

	if (s.indexOf('..') !== -1) {
		// a domain should never have two sequential dots because only one dot is used between subdomains
		return false;
	}

	if (s.length > 255) {
		// domain part is too long
		return false;
	}

	var domain_parts = s.split('.');

	if (domain_parts.length < 2) {
		// must be at least 2 parts, domain.tld
		// can include subdomains
		return false
	}

	var tld = domain_parts[domain_parts.length - 1];

	if (tld.length < 2 || tld.length > 63) {
		// tld must be 2-63 characters long
		return false;
	}

	var tld_m = tld.match(/[\p{L}]/gu);
	if (tld_m === null) {
		// all invalid
		return false;
	} else if (tld_m.length !== tld.length) {
		// tld must be letters only
		return false;
	}

	// domains contain letters, digits hyphens and dots
	var domains = domain_parts.slice(0, domain_parts.length-1);

	var c = 0;
	while (c < domains.length) {

		var domain_m = domains[c].match(/[\p{L}\p{N}-]/gu);
		if (domain_m === null) {
			// all invalid characters in domain part
			return false;
		} else if (domain_m.length !== domains[c].length) {
			// invalid characters in domain part
			return false;
		} else if (domains[c][0] === '-' || domains[c][domains[c].length - 1] === '-') {
			// - must not be the first or last character
			return false;
		} else if (domains[c].length > 63) {
			// must be 63 characters or less
			return false;
		}

		c++;

	}

	return true;

}