Do Functions, Strings, and Numbers Actually Behave Like Objects in JavaScript?

Are Functions, Strings, and Numbers Objects in JavaScript?

JavaScript's reputation for declaring almost everything as an object can be puzzling, especially for beginners. While it's true that objects, with their methods and properties, play a significant role, primitives like strings, numbers, and functions behave somewhat differently.

Primitive Values vs. Objects

In JavaScript, primitive values are immutable and can't be accessed through dot notation. However, JavaScript provides wrapper objects (String, Number, and Boolean) that endow primitives with object-like methods and properties.

Wrapper Objects

Wrapper objects are created behind the scenes when accessing properties of primitives. For instance, in the code:

var s = "foo";
var sub = s.substring(1, 2);

JavaScript silently creates a String object, calls the substring() method, and then discards the object. The sub variable now contains the primitive string "o."

While it may appear that you can assign properties to primitives, these assignments are actually performed on the wrapper objects that are discarded immediately. Therefore, retrieving such properties yields undefined, as demonstrated in the following example:

var s = "foo";
s.bar = "cheese";
alert(s.bar); // undefined

Functions as Objects

Unlike primitives, functions are full-fledged objects that inherit from Object. They can have properties, as seen in this code:

function foo() {}
foo.bar = "tea";
alert(foo.bar); // tea

In summary, primitives do not inherently have object characteristics in JavaScript. However, wrapper objects provide a facade of object-like behavior, while functions are true objects that can interact with properties and methods. This distinction is essential for understanding JavaScript's type system and making informed coding decisions.

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