Beneath Classes: Prototypes

Classes.js

class Spiderman {
  lookOut() {
    alert('My Spider-Sense is tingling.');
  }
}

let miles = new Spiderman();
miles.lookOut();

Prototypes.js

// class Spiderman {
let SpidermanPrototype = {
  lookOut() {
    alert('My Spider-Sense is tingling.');
  }
};

// let miles = new Spiderman();
let miles = { __proto__: SpidermanPrototype };
miles.lookOut();

Love this content, thank you for sharing it freely with us all Dan!

This is picked up from the Typescript playground. I just finished the Just Javascript module written by Dan and I have a question which might be a noob one but isn't Spiderman.prototype.lookOut = (..) regarded as polluting the prototype and should be discouraged?

@ovistoica typescript is probably converting it like that for compatibility and performance reasons. But people are discouraged to use it.

@ovistoica I think it is not exactly polluting, because It isn't changing a default prototype like Array, String or Object ones.

Hi @gaearon,

I am wondering why, when defining classes, the properties are on the object itself while the methods are on the __proto__

class Spiderman {
  aProperty;
  lookOut() {
    alert("My Spider-Sense is tingling.");
  }
}

let miles = new Spiderman();
console.log(miles.hasOwnProperty("aProperty")); // true
console.log(Object.getPrototypeOf(miles).hasOwnProperty("lookOut")); // true

This is picked up from the Typescript playground. I just finished the Just Javascript module written by Dan and I have a question which might be a noob one but isn't Spiderman.prototype.lookOut = (..) regarded as polluting the prototype and should be discouraged?

const someObject = {};
const everyObjectProto = someObject.__proto__;
const someFunction = function() {};
someFunction.prototype.__proto__ === everyObjectProto; // true

So "someFunction.prototype" points to an object, just like any other in your code, not to the "main" object prototype. Thus it is not polluting anything.

This is picked up from the Typescript playground. I just finished the Just Javascript module written by Dan and I have a question which might be a noob one but isn't `Spiderman.prototype.lookOut = (..)` regarded as polluting the prototype and should be discouraged?

const someObject = {}; const everyObjectProto = someObject.proto; const someFunction = function() {}; someFunction.prototype.proto === everyObjectProto; // true

So "someFunction.prototype" points to an object, just like any other in your code, not to the "main" object prototype. Thus it is not polluting anything.

This someFunction.prototype.__proto__ === everyObjectProto; // true can be changed to someFunction.prototype === everyObjectProto; // false for clarity