Question

If numbers are primitive types, why I can do:

> (12345).toString()
"12345"

Is the parenthesis converting the primitive type to a Number?

Answer 1

No, the parentheses are just letting the parser understand that the . is not a decimal point.

12345 .toString() will also work.

Primitive numbers implicitly converted to Numbers whenever you access their properties, but the objects are temporary and immediately lost. For example:

var foo = 5;

foo.bar = "something";

console.log(foo.bar); // undefined

Same goes for strings and booleans.