Why does instanceof return false for some literals?

Question

"foo" instanceof String //=> false
"foo" instanceof Object //=> false

true instanceof Boolean //=> false
true instanceof Object //=>         


        

Answer 1

This is defined in the ECMAScript specification Section 7.3.19 Step 3: If Type(O) is not Object, return false.

In other word, if the Obj in Obj instanceof Callable is not an object, the instanceof will short-circuit to false directly.