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?