ReactJS中this._newText是什么？是否为React专属特性？

Hey there! Great question—let’s break down that code and clarify whether this is a React-specific feature.

First off: Yes, this is absolutely a React-exclusive pattern, specifically called a callback ref. Let’s unpack what’s happening here:

What’s the code doing? #

Your code uses a callback function (written as an ES6 arrow function) assigned to the ref prop of the <textarea> element:

<textarea ref={input => this._newText = input}/>

When the React component mounts, React automatically passes the actual DOM node of the <textarea> as the input argument to this callback. You then store that DOM node in this._newText, letting you directly access and manipulate the textarea’s DOM element later (like reading its value, focusing it, etc.).

When the component unmounts, React will call this callback again—but this time with null as the argument. This helps prevent memory leaks by clearing your reference to the DOM node once it’s no longer in the DOM.

How does this fit with other React ref approaches? #

React has a few ways to handle refs:

• String refs (old, deprecated): <textarea ref="newText"/> (you’d access it via this.refs.newText, but this is no longer recommended due to reliability issues).
• createRef() (for class components): You’d create a ref instance with this.newText = React.createRef() and use it as <textarea ref={this.newText}/>, accessing the DOM node via this.newText.current.
• Callback refs (the one in your code): This is a more flexible option—you can do custom logic when the ref is attached or detached, like logging, or conditionally setting the ref.

Wait, is the arrow function part of React? #

The arrow function itself is an ES6 JavaScript feature, not React-specific. But using it as a callback for the ref prop to capture DOM elements is a React-specific mechanism. React manages when this callback is called (on mount, update, and unmount) to ensure you always have the correct reference to the DOM node.

So to recap: The syntax of the arrow function is vanilla JS, but using it in the ref prop to get a DOM reference is a React-exclusive feature that gives you direct access to DOM elements in your React components.

内容的提问来源于stack exchange，提问作者Alex Ironside