"==" vs. "==="

In notebook:
FrontEndMasters Advanced JS fundamentals
Created at:
2015-10-08
Updated:
2015-10-08
Tags:
Fundamentals JavaScript
Learn JS Fundamentals to jQuery & Pure DOM Scriptingsome strange stuff
  21 == "21" // true
undefined == null // true
undefined === null // false
21 === 21 // true
{} === {} // false
NaN === NaN // false
true = {valueOf: function(){return "1"}} // true