is_email function from WordPress written in Javascript

is_email.js

/**
 * is_email function from WordPress
 *    written in Javascript
 * 
 * by Louy Alakkad <me@l0uy.com>
 * 
 * Verifies that an email is valid.
 *
 * Does not grok i18n domains. Not RFC compliant.
 *
 * @param string $email Email address to verify.
 * @return string|bool Either false or the valid email address.
 */
function is_email( $email ) {
	// Test for the minimum length the email can be
	if ( $email.length < 3 ) {
		return false;
	}

	// Test for a single @ character after the first position
	if ( $email.indexOf('@') === -1 || $email.indexOf('@') !== $email.lastIndexOf('@') ) {
		return false;
	}

	// Split out the local and domain parts
	var parts = $email.split('@',2);
	var $local = parts[0], $domain = parts[1];

	// LOCAL PART
	// Test for invalid characters
	if ( !/^[a-zA-Z0-9!#$%&\'*+\/=?^_`{|}~\.-]+$/.test($local) ) {
		return false;
	}

	// DOMAIN PART
	// Test for sequences of periods
	if ( /\.{2,}/.test($domain) ) {
		return false;
	}

	// Test for leading and trailing periods and whitespace
	if ( str_trim( $domain, " \t\n\r\0\x0B." ) !== $domain ) {
		return false;
	}

	// Split the domain into subs
	var $subs = $domain.split( '.' );

	// Assume the domain will have at least two subs
	if ( 2 > $subs.length ) {
		return false;
	}

	// Loop through each sub
	for ( i in $subs ) {
		var $sub = $subs[i];
		// Test for leading and trailing hyphens and whitespace
		if ( str_trim( $sub, " \t\n\r\0\x0B-" ) !== $sub ) {
			return false;
		}

		// Test for invalid characters
		if ( !/^[a-z0-9-]+$/i.test( $sub ) ) {
			return false;
		}
	}

	// Congratulations your email made it!
	return $email;
	
	function str_trim(str, regex) {
		var chr = regex.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|\:\!\,\=]/g, "\\$&");
		return str.replace( new RegExp('/^['+chr+']*/'), '' ).replace( new RegExp('/['+chr+']*$/'), '' );
	}
}

Thank you for saving me the hassle of translating that!

The str_trim() function doesn't seem to work correctly - it doesn't remove leading/trailing hyphens, so it allows dave@abc.x- through as a valid email, which is then rejected by WordPress.

I replaced it with this function which seems to work: http://phpjs.org/functions/trim/

Hi. @davejamesmiller thank you a lot!

@davejamesmiller That function still appears to let dave@abc.x- through.