== and === are common stumbling blocks especially for JavaScript beginners. It is important to know that == comparison coerces values whereas === does not. Just to give you an idea of what this means. Consider the following cases:
0 == '' // true
0 === '' // false
I know it might seem like a trivial detail but it is not. Used right it can be a useful feature. In worst case this behavior can introduce subtle and difficult to detect bugs.