First, take note of these 3 statements :
- All objects have a prototype.
- The prototype is another object that the original object inherits from.
- The original object has access to all of its prototype’s methods and properties
Nothing seems to make sense for now. Let me guide you.
What is a prototype?
View this article at Digital Ocean for more info.
Every object in JS has an internal property called [[Prototype]]. It creates a way for two or more objects to be linked together.
We can’t access it directly; instead we use the getPrototypeOf() method.
let x = {};
Object.getPrototypeOf(x);
When we put this in the browser console :
Another way to do so is through x.__proto__.
__proto__ is depreciated and shouldn’t be used at all!
Prototypal inheritance
There are 2 reasons why we define properties and functions on the prototype :
One, to have common properties and functions to save memory.
Two, to have prototypal inheritance.
It just means our objects inherit from the className.prototype object which allows them to access functions and properties defined in it. The prototype object is itself inheriting from Object.prototype, thus forming a chain of inheritances.
hasOwnProperty() tells you if an object [or prototype] has a property :
pOne.hasOwnProperty('loc'); //true
pOne.hasOwnProperty('valueOf'); //false
Object.prototype.hasOwnProperty('valueOf'); //true
Object.prototype.hasOwnProperty('hasOwnProperty'); //true