JavaScript style: don't use wrapper objects for primitive types

Question

In the Google JavaScript style guide, it says not to use wrapper objects for primitive types. It says it's "dangerous" to do so. To prove its point, it uses the example:

var x = new Boolean(false);
if (x) {
  alert('hi');  // Shows 'hi'.
}

OK, I give up. Why is the if code being executed here?

Answer 1

if(x) will run if x is truthy.

x is truthy if it's not falsey.

x is falsey if x is null, undefined, 0, "", false

So since new Boolean(false) is an Object and an Object is truthy, the block runs

Answer 2

Because every variable that is typeof Object is truthy and wrappers are objects.