JavaScript - Why can't I add new attributes to a “string” object?

Question

I\'ve experimented with JavaScript and noticed this strange thing:

var s = \"hello world!\";
s.x = 5;
console.log(s.x); //undefined

Every t

Answer 1

String objects are objects and can be expanded, but string literals are not string objects and can not be expanded.

Example:

var s = 'asdf';
s.x = 42;
alert(s.x); // shows "undefined"

s = new String('asdf');
s.x = 1337;
alert(s.x); // shows "1337"