Validate URL 檢查URL是否有效

ValidateURL.as

package
{
	/**
	 * @link http://stackoverflow.com/questions/3455448/regex-url-problem
	 * @param	_url
	 * @return
	 */
	public function ValidateURL(_url:String):String
	{
		var pattern:RegExp = new RegExp(
			"\\b((?:https?://|www\\d{0,3}[.]|[a-z0-9.\\-]+[.][a-z]{2,4}/)"+
			"(?:[^\\s()<>]+|\\(([^\\s()<>]+|(\\([^\s()<>]+\\)))*\\))+"+
			"(?:\\(([^\\s()<>]+|(\\([^\\s()<>]+\\)))*\\)|"+
			"[^\\s`!()\\[\\]{};:'\".,<>?«»“”‘’]))",
			"i" // case insensitive
		)
		var match:Array = _url.match(pattern);
		if (match) {
			return match[1];
		}else {
			return null;
		}
	}
}