JavaScript類(lèi)與原型的核心區(qū)別在於，類(lèi)是ES6引入的語(yǔ)法糖，底層仍基於原型機(jī)制。 1. 類(lèi)提供更清晰的面向?qū)ο笳Z(yǔ)法，使代碼更易讀；2. 原型是JavaScript實(shí)現(xiàn)繼承和方法共享的實(shí)際機(jī)制；3. 類(lèi)本質(zhì)上是特殊函數(shù)，其方法被添加到構(gòu)造函數(shù)的原型上；4. 原型支持運(yùn)行時(shí)動(dòng)態(tài)修改，更加靈活但需謹(jǐn)慎使用；5. 類(lèi)默認(rèn)使用嚴(yán)格模式且不提升，而原型方式更貼近語(yǔ)言本質(zhì)。理解兩者關(guān)係有助於更好地掌握J(rèn)avaScript的面向?qū)ο缶幊獭?

If you're diving into object-oriented JavaScript, one of the first things you'll run into is the difference between classes and prototypes. JavaScript didn't originally have classes — it used prototypes from the beginning. Classes were added later in ES6 as a cleaner way to work with prototype-based code. But under the hood, even classes still rely on prototypes. So what's really going on here?

How JavaScript Classes Work Under the Hood

When ES6 introduced class syntax, it made object-oriented code look more familiar to developers coming from other languages like Java or Python. But behind that neat class , constructor , and extends syntax, JavaScript is still using its prototype system.

A class in JavaScript is essentially a special kind of function. When you define a class, you're creating a constructor function that gets called when you use new . All the methods you write inside the class body are added to the constructor's prototype.

For example:

 class Dog {
  constructor(name) {
    this.name = name;
  }

  bark() {
    console.log('Woof!');
  }
}

This is almost equivalent to writing:

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

Dog.prototype.bark = function() {
  console.log('Woof!');
};

So while the syntax is different, the behavior is very similar — both approaches attach methods to the prototype.

Prototypes Are the Real Building Block

Before ES6, everything in JavaScript was based on objects and prototypes. There was no formal "class" definition — instead, you created objects and then linked other objects to them via a prototype chain.

The prototype model works by delegation: if an object doesn't have a certain property or method, JavaScript looks up its prototype chain until it finds it (or returns undefined ). That's how multiple instances can share the same method without each having their own copy.

You can manually set the prototype using Object.create() :

 const animal = {
  eat() {
    console.log('Eating...');
  }
};

const dog = Object.create(animal);
dog.bark = function() {
  console.log('Woof!');
};

Now, dog has access to both bark() and eat() because animal is its prototype.

One big difference is flexibility — with prototypes, you can change behavior at runtime by modifying the prototype directly, which can be powerful but also risky if not handled carefully.

Key Differences Between Classes and Prototypes

Even though classes are built on prototypes, there are some important differences:

• Syntax and Readability : Classes offer a cleaner, more structured way to define object types, especially when dealing with inheritance.
• Hoisting : Function declarations (used for pre-ES6 constructor functions) are hoisted, but class declarations are not — you must declare a class before using it.
• Strict Mode : Class bodies always execute in strict mode, even if you don't specify it.
• Inheritance with extends : While you can simulate inheritance with prototypes using Object.create() , classes make this much simpler with the extends keyword and super() call.

Also, classes encourage a more traditional OOP style, while prototypes expose the underlying mechanism and allow for more dynamic object creation patterns.

Which Should You Use?

If you're working on a modern codebase or collaborating with others who are used to class-based languages, stick with class syntax — it's clearer and less error-prone.

But if you want a deeper understanding of how JavaScript actually works — or need to optimize memory usage by sharing methods across many instances — learning the prototype model is essential.

It's also worth noting that you don't have to pick one over the other completely. Many experienced developers mix both styles depending on the situation.

Some points to consider:

• If you're building large-scale applications, classes help keep your code organized.
• For small utilities or performance-sensitive code, working directly with prototypes might give you more control.
• Understanding both helps you debug issues related to the prototype chain or inheritance.

At the end of the day, classes and prototypes aren't opposites — they're two sides of the same coin in JavaScript. Knowing how they connect makes you a stronger developer, whether you're reading legacy code or writing new modules today.

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