What is a good regular expression to match a URL? [duplicate]

Currently I have an input box which will detect the URL and parse the data.

So right now, I am using:

var urlR = /^(?:([A-Za-z]+):)?(\/{0,3})([0-9.\-A-Za-z]+)
           (?::(\d+))?(?:\/([^?#]*))?(?:\?([^#]*))?(?:#(.*))?$/;
var url= content.match(urlR);

The problem is, when I enter a URL like www.google.com, its not working. when I entered http://www.google.com, it is working.

I am not very fluent in regular expressions. Can anyone help me?

Regex if you want to ensure URL starts with HTTP/HTTPS:

https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)

If you do not require HTTP protocol:

[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)

To try this out see http://regexr.com?37i6s, or for a version which is less restrictive http://regexr.com/3e6m0.

Example JavaScript implementation:

var expression = /[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)?/gi;
var regex = new RegExp(expression);
var t="www.google.com";

if (t.match(regex)) {
  alert("Successful match");
} else {
  alert("No match");
}