检查JavaScript字符串是否为URL

与答案相关的问题：

或来自Devshed的此正则表达式：

function validURL(str) {  var pattern = new RegExp('^(https?:\/\/)?'+ // protocol    '((([a-z\d]([a-z\d-]*[a-z\d])*)\.)+[a-z]{2,}|'+ // domain name    '((\d{1,3}\.){3}\d{1,3}))'+ // OR ip (v4) address    '(\:\d+)?(\/[-a-z\d%_.~+]*)*'+ // port and path    '(\?[;&a-z\d%_.~+=-]*)?'+ // query string    '(\#[-a-z\d_]*)?$','i'); // fragment locator  return !!pattern.test(str);}