Search code examples
javascriptoopmethodspropertiesinstances

Question about Javascript properties and instances

I can't figure out myself why foo.bar in the example is undefined, could you explain?

var foo = "foo";

foo.bar = "baz";
console.log(foo.bar); // undefined

Q2: How do I add references to properties and methods to the String instance foo?

Help is appreciated, thanks.

-- EDIT --

Note: the question is about a generic String instance, not the String global object. So using "classic" prototyping as someone suggested is not an option, because this way every String instance would have a property called bar, while I want to augment only certain instances.

Solution

  • This is a duplicate of Why can't I add properties to a string object in javascript?.

    Basically, you're creating a string, and this is a primitive type in javascript.

    You cannot add properties to primitive types in javascript.