console.log is not working when used in a Firefox, Greasemonkey script

My userscript prints some information using console.log().

This works fine in Chrome, but when I install this userscript in Firefox (Greasemonkey), the web console in Firefox is not displaying anything.

I searched for a solution and some suggested to use unsafeWindow but it is also not showing any output. Moreover unsafeWindow cannot be used for chrome. I even installed Firebug but it was no use. How can I resolve this?

For example, I tried this userscript in Firefox:

// ==UserScript==
// @name        console
// ==UserScript==
console.log("hello");