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

Or you can just make your own function like so:

function isInstanceOf(obj, clazz){
  return (obj instanceof eval("("+clazz+")")) || (typeof obj == clazz.toLowerCase());
};

usage:

isInstanceOf('','String');
isInstanceOf(new String(), 'String');

These should both return true.