How can I create a unique session ID like in JSFiddle?

I would like to create a unique session url for each connection on my website like on JSFiddle

I'm using NodeJS and Express.

The result should be as follow:

for members:

https://mywebsite.com/user/uniqueID/
*eg : https://mywebsite.com/user/o2gxgz9r/*

for guests:

https://mywebsite.com/uniqueID/
eg : *https://mywebsite.com/k36yot0z/*

How can I achieve that and is there any specific frameworks for this kind of job?

via JSmith