Creating functions using `Object.create`

Question

I am learning JavaScript and I am having trouble understanding a certain aspect of functions. For example, I know that I can create an array using Object.create like this:

const array = Object.create(Array.prototype);

Since functions are also objects in JavaScript, I'm wondering if it's possible to create a function using Object.create in a similar way?

Answer 1

It is not possible.

Object.create is merely a convenience function to configure prototype chains and define own properties.

The key distinguishing characteristic of functions is the existence of the non-userland [[Call]] internal method, invokeable with the identifier(<arguments>) syntax. The only ways I know to configure an object to have this internal method are:

1. to use the usual function-object creation syntaxes (eg. function() {}, () => {}), or
2. Use the Function constructor, or
3. Use classes and extend Function.

const f = Object.create(Function.prototype)
console.log(typeof f) // 'object' (not 'function') 

Answer 2

Object.create is not intended for creating functions directly but is used for creating objects with specific prototypes.

To create a function in JavaScript, you can use the function declaration or function expression syntax.

In JavaScript, functions are considered "first-class objects," meaning they are treated as objects and have properties and methods like any other object. This behavior is due to JavaScript's support for higher-order functions and its functional programming capabilities.

Here are a few reasons why functions are considered objects in JavaScript:

1. Functions are instances of the Function constructor: In JavaScript, functions are created using the Function constructor or function declarations/expressions. The Function constructor itself is an object, and when you create a function, you are essentially creating an instance of that object.
2. Functions can have properties: Like any object, functions can have properties assigned to them. You can add custom properties to a function, access or modify them, and even delete them.
3. Functions can be passed as arguments and returned from other functions: In JavaScript, functions can be passed as arguments to other functions and returned as values from functions. This behavior is a fundamental characteristic of higher-order functions and is closely tied to the concept of functions being objects.
4. Functions have built-in properties and methods: In addition to custom properties, functions in JavaScript have built-in properties and methods. For example, they have properties like name and length, which provide information about the function, and methods like call(), apply(), and bind(), which allow you to control the function's execution context.

function myFunction() {
  // Function code here
}

myFunction.customProperty = 'Hello';

console.log(myFunction.customProperty);