Prototypal inheritance is a language feature that helps in that.… [[Prototype]].In JavaScript, objects have a special hidden property [[Prototype]] (as named in the specification… In programming, this is called “prototypal inheritance”.… It’s a getter/setter for [[Prototype]].… The object referenced by [[Prototype]] is called a “prototype”.
The "prototype" property is widely used by the core of JavaScript itself.… And there are no corresponding prototypes either.… Changing native prototypes.Native prototypes can be modified.… So, generally, modifying a native prototype is considered a bad idea.… Some methods of native prototypes are often borrowed.
Setting or reading the prototype with obj.… The modern methods to get/set a prototype are:
Object.getPrototypeOf(obj) – returns the [[Prototype]… [[Prototype]] at any time.… [[Prototype]].… it is not [[Prototype]] itself.
If F.prototype is an object, then the new operator uses it to set [[Prototype]] for the new object.… Please note:
JavaScript had prototypal inheritance from the beginning.… Please note that F.prototype here means a regular property named "prototype" on F.… Yes, it exists in the default "prototype" for functions, but that’s all.… ]]) sets [[Prototype]] of new objects when new F() is called.
Again, using prototypes.… As you might have already guessed, extends gives Rabbit the [[Prototype]] reference to Animal.… So, Rabbit extends Animal creates two [[Prototype]] references:
Rabbit function prototypally inherits… Rabbit.prototype prototypally inherits from Animal.prototype.… For class B extends A the prototype of the class B itself points to A: B.[[Prototype]] = A.
That’s because Array prototypically inherits from Object.… Normally, instanceof examines the prototype chain for the check.… in the obj prototype chain.… Only the chain of prototypes and Class.prototype matters.… That can lead to interesting consequences when a prototype property is changed after the object is created
There can be only one [[Prototype]] for an object. And a class may extend only one other class.… mixin in JavaScript is to make an object with useful methods, so that we can easily merge them into a prototype… parent method super.say() from sayHiMixin (at lines labelled with (*)) looks for the method in the prototype… [[Prototype]], that means it searches sayHiMixin.[[Prototype]].… JavaScript does not support multiple inheritance, but mixins can be implemented by copying methods into prototype
[[Prototype]] to Animal.prototype.… Its prototype, that is Rabbit.prototype (has hide, but not run).… As we can recall from the chapter Native prototypes, JavaScript itself uses prototypal inheritance for… [[Prototype]] is Object.prototype.… Then super uses it to resolve the parent prototype and its methods.
After new User object is created, when we call its method, it’s taken from the prototype, just as described… indeed reasons why class can be considered a syntactic sugar to define a constructor together with its prototype… A class definition sets enumerable flag to false for all methods in the "prototype".
[[Prototype]] does not reference Object, so there’s no, for instance, Array.keys() (or Date.keys()) static
…So we need either to filter fields from the prototype… The latter works, because Object.keys only returns the keys that belong to the object, ignoring the prototype
In other words, reading prototype of a proxy must always return the prototype of the target object.… Property flags and descriptors).
for..in loops over non-symbol keys with enumerable flag, and also prototype… When we read admin.name, as admin object doesn’t have such own property, the search goes to its prototype… The prototype is userProxy.
After we learn that, we return to objects and cover them in-depth in the chapters Prototypes, inheritance
We can also modify built-in prototypes
They use prototype-based classes for inheritance.