在react中的生命周期方法之外添加类名

class MyComponent extends React.Component {
  constructor(props) {
    super(props);
    this.myRef = React.createRef();
  }

  componentDidMount() {
    this.myRef.current.classList.add('my-class');
  }

  render() {
    return <div ref={this.myRef}>Hello, World!</div>;
  }
}

class MyComponent extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      className: 'my-class'
    };
  }

  render() {
    return <div className={this.state.className}>Hello, World!</div>;
  }
}

npm install classnames

import classNames from 'classnames';

class MyComponent extends React.Component {
  render() {
    const className = classNames('my-class', {
      'another-class': this.props.condition
    });

    return <div className={className}>Hello, World!</div>;
  }
}