JavaScript Prototypes

From Greek:

• prōto- = “first”
• typos = “impression, model, pattern, or stamp”

Prototypes are the way inheritance is handled in JavaScript. Every JS Object has a prototype. The prototype again is also set to an Object. => Prototype Chain
The chain ends when a prototype is set to null.

graph LR

A["const nums = [1, 2, 3]"]:::main
A-->|prototype|B[Array]
B-->|prototype|C[Object]
C-->|prototype|D[null]

__proto__ vs prototype

prototype is defined on the constructor of an object. __proto__ is defined on the instance of the object.

function Person(name) {
  this.name = name;
}

const bob = new Person("Bob");

bob.__proto__ === Person.prototype // true