Comparing function declaration

I wanted to check whether a variable has a value (in my case function). I started to playing around in node cli and I found weird results:

Cases:

• (function(){} == true) // returns false
• (function(){} == false) // returns false
• (!function(){} == true) // returns false
• (!function(){} == false) // returns false
• ((function(){}) == true) // returns false
• (!(function(){}) == true) // returns false
• (!!function(){} == true) // returns true
• (!!function(){} == false) // returns false
• Boolean(function(){}) // returns true

Can somebody explain why something like this happens?

Looks like correct boolean value is true for function(){}, but it returns false.

PS. In case my nodejs version - v5.8.0