ECMAScript 6是否鼓励在JavaScript中使用经典继承？

Question

I've come across many proponents of true prototypical inheritance in JavaScript (as opposed to constructor inheritance). They suggest the new keyword shouldn't be used as it prevents the use of functional programming in the language.

Does ES6 encourage the use of classical inheritance? Considering the fact that it introduces the keyword class (called with the new keyword).

Answer 1

The article is outdated. The problem of not being able to use .apply() with new is solved as of ECMAScript 6. You can now use spread syntax: new Person(...args) .

The new class syntax enhances prototypal inheritance by providing better code organization, neater syntax and some capabilities that were previously not possible. Even though it uses the keyword class , it has nothing to do with classical inheritance as found in Java, C++, etc..

No matter what you decide to use, endeavor to write clear, understandable, maintainable code, and you'll do well.

Answer 2

There are many patterns to achieve inheritance in JS. ES6 classes are just syntactic sugar for one of them.

ECMAScript 6 is still JavaScript and doesn't encourage any particular paradigm. However, there are practical considerations that are suggested by ES6 classes, which are idiomatic solution for inheritance in ES6.

When ES6 classes are inherited by non-ES6 classes, bad things may happen:

class Es6Class {}

function Es5Class() {
  var _this = Object.create(Es6Class.prototype);
  _this = Es6Class.apply(_this, arguments);
  return _this;
}

This is natural to call a constructor with call or apply and existing context on construction (this is roughly what happens when ES6 classes are transpiled with Babel or Typescript). But ES6 classes have built-in protection against calling them without new , so Es5Class will fail.

Another problem appears when ES5 classes that implement random inheritance recipe are inherited by ES6 classes (as shown in this React question ):

function Es5ClassWithShallowPrototypeChain() {
  var _this = {};
  _this = AnotherEs5Class.call(_this, arguments);
  _this.method = function () {};
}

class Es6Class {
  method() {}
}

In code above it's expected that Es6Class will override method but this won't happen, because method is instance method ( this.method ) in Es5ClassWithShallowPrototypeChain and prototype method ( this.__proto__method ) in Es6Class .

A developer is free to choose any inheritance recipe he/she is comfortable but should always take into account how the recipe will affect third-party code. While ES6 class inheritance implementation is idiomatic to JS and generally can be used as a rule of thumb in ES6 code.

Answer 3

I would say yes, it does. As far as I know, it is still prototypical inheritance under the hood; the class keyword formalizes a common design pattern. This article covers this:
Better JavaScript with ES6, Pt. II: A Deep Dive into Classes

You can still do functional programming in JavaScript , but overall, the JS community seems to be moving away from that and more toward a classical object-oriented programming style.