React类组件bind方法疑问：Codeacademy课程代码未绑定却可行？

Hey there! I totally get where you’re coming from—this this binding stuff in React class components can feel super confusing at first, especially when examples seem to contradict each other. Let’s break down why you might see a scream method working without a .bind() call, and what that "don’t do this" note in later exercises is referring to.

Why the unbound scream method might work #

There are two common scenarios where you don’t need to explicitly bind a class method in React:

• You’re using an arrow function to define the method
  If your scream method is written like this (using class field syntax):

  class MyComponent extends React.Component {
    scream = () => {
      console.log(this.state.message);
    }
  
    render() {
      return <button onClick={this.scream}>Scream</button>;
    }
  }
  

  Arrow functions don’t have their own this—they inherit the this from the surrounding scope (in this case, the component instance). So this inside scream will automatically point to your component, no .bind() needed. This syntax is widely used now, but older tutorials might focus more on manual binding because class fields were experimental when React first gained popularity.

• You’re wrapping the method call in an arrow function when using it
  Even if scream is a regular class method, you might see it used like this in the render method:

  render() {
    return <button onClick={() => this.scream()}>Scream</button>;
  }
  

  Here, the arrow function captures the component’s this context, so when it calls this.scream(), this inside scream will be the component instance. Note that this creates a new function every time the component renders, which is fine for small components but can cause performance issues in larger apps.

What the "don’t do this" note is referring to #

The later exercise is probably warning against passing an unbound regular method directly as an event handler, like this:

class MyComponent extends React.Component {
  scream() {
    console.log(this.state.message); // This will throw an error!
  }

  render() {
    return <button onClick={this.scream}>Scream</button>; // Bad practice (without binding)
  }
}

In strict mode (which React uses by default), a regular class method’s this is undefined when called as a callback. So clicking the button here would cause an error because this isn’t pointing to the component instance. That’s why you need to either bind it in the constructor, use an arrow function method, or wrap the call in an arrow function.

Quick recap to clear up confusion #

• Regular class methods need manual binding (via constructor .bind(), arrow function wrapper, or class field arrow function) to access the component’s this.
• Arrow function class methods skip the need for manual binding entirely.
• The "don’t do this" rule applies to unbound regular methods passed directly as event handlers—not all cases where .bind() isn’t visible.

Hope this clears up the missing piece for you! 🚀

内容的提问来源于stack exchange，提问作者Trigosin Darom