React Memo Example

index.html

<div id="root"></div>

react-memo-example.markdown

React Memo Example

React.memo can help you control what components re-render. It's like a PureComponent in the Class syntax, only this is for function components.

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License.

script.babel

const ChildOne = React.memo(props => {
  console.log("Rerendering Child One");
  return(
    <div className="box">
      <h2>Hello! {props.name}</h2>
      <p>This component won't re-render, check your console.</p>
    </div>
  )
});

const ChildTwo = (props) => {
  console.log('Rerendering Child Two')
  return (
    <div className="box">
      <h2>Hello! {props.name}</h2>
      <p>This component will render re-render, check your console.</p>
    </div>
  )
}

class App extends React.Component {
  state = {
    value: 1,
    name: "Chris"
  };

  handleClick = () => {
    this.setState({
      value: this.state.value + 1
    });
  };

  render() {
    return (
      <React.Fragment>
        <div className="box">
          <div>{this.state.value}</div>
          <button onClick={this.handleClick}>+</button>
        </div>
        <ChildOne name={this.state.name} />
        <ChildTwo name={this.state.name} />
      </React.Fragment>
    );
  }
}

ReactDOM.render(<App />,
document.getElementById("root"))

scripts

<script src="https://unpkg.com/[email protected]/umd/react.production.min.js"></script>
<script src="https://unpkg.com/[email protected]/umd/react-dom.production.min.js"></script>

style.scss

body {
  height: 100vh;
  margin: 0;
  display: grid;
  place-items: center;
}
.box {
  width: 300px;
  h1 {
    font-size: 20px;
    margin: 0 0 1rem 0;
  }
}

styles

<link href="https://cdnjs.cloudflare.com/ajax/libs/bulma/0.7.4/css/bulma.min.css" rel="stylesheet" />

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