gistfile1.js

// be careful with those implicit .toString() calls in == comparison

typeof "abc" == "string"    // true
typeof String("abc") == "string"    // true
String("abc") == "abc"   // true -- same types get casted to equal each other

String("abc") instanceof String    // false -- hmmm...
(new String("abc")) instanceof String   // true
String("abc") == (new String("abc"))    // true -- wait, wtf?

String("abc") == "abc" // true -- same types get casted to equal each other

That's not casting.

As you can see further down String("abc") doesn't return an object that's an instance of String. You'd obviously need to do new String("abc") for that.

Without new, String("abc") simply returns a string, not an instance of String. That's why String(5) === '5'