what are refs in react code example

Example 1: when to use react ref

WHEN TO USE REACT'S REF ATTRIBUTE?
But it is not always a good idea to use the ref attribute. The general rule of thumb is to avoid it. The official React documentation mentions three occasions where you can use it because you have no other choice.

Managing focus, text selection, or media playback.
Integrating with third-party DOM libraries.
Triggering imperative animations.

Example 2: refs react js

class Lesson9Refs extends Component {

    onAddProduct = () => {
        alert(this.refs.productname.value);
    }
    
    
    return (

            <div>

                <div className="container">
                    <div class="card mt-10">
                        <div class="card-header">
                            Featured
                        </div>
                        <div class="card-body">
                          
                            <label> Product Name: </label>
                            <input type='text' className="form-control" ref="productname" />  

                            <button type="submit" className="btn btn-primary" onClick={ this.onAddProduct } >
                                Add Product
                            </button>

                        </div>
                    </div>
                    <div className="row mt-10">
                        { elements }
                    </div>
                </div>
            </div>
        );

    }
}

export default Lesson9Refs;

Example 3: cre&atRefs react js

const node = this.myRef.current;

Example 4: use ref in component reactjs

function MyFunctionComponent() {  return <input />;
}

class Parent extends React.Component {
  constructor(props) {
    super(props);
    this.textInput = React.createRef();  }
  render() {
    // Ça ne fonctionnera pas !
    return (
      <MyFunctionComponent ref={this.textInput} />    );
  }
}

Example 5: use ref in component reactjs

function CustomTextInput(props) {
  // textInput doit être déclaré ici pour que la ref puisse s’y référer  const textInput = useRef(null);
  function handleClick() {
    textInput.current.focus();  }

  return (
    <div>
      <input
        type="text"
        ref={textInput} />      <input
        type="button"
        value="Donner le focus au champ texte"
        onClick={handleClick}
      />
    </div>
  );
}

Example 6: use ref in component reactjs

class CustomTextInput extends React.Component {
  constructor(props) {
    super(props);

    this.textInput = null;
    this.setTextInputRef = element => {      this.textInput = element;    };
    this.focusTextInput = () => {      // Donne le focus au champ texte en utilisant l’API DOM native.      if (this.textInput) this.textInput.focus();    };  }

  componentDidMount() {
    // Focus automatique sur le champ au montage
    this.focusTextInput();  }

  render() {
    // Utilise la fonction de rappel `ref` pour stocker une référence à l’élément
    // DOM du champ texte dans une propriété d’instance (ex. this.textInput)
    return (
      <div>
        <input
          type="text"
          ref={this.setTextInputRef}        />
        <input
          type="button"
          value="Donner le focus au champ texte"
          onClick={this.focusTextInput}        />
      </div>
    );
  }
}