focus

중간에 포커스 해주는 부분을 넣지 않아도 그냥 포커스가 되는데요. 이게 다른 이유 ( 제 브라우저, 아님 익스텐션 때문에) 때문일수도 있을까요?

<html>
  <head>
    <script crossorigin src="https://unpkg.com/react@16/umd/react.development.js"></script>
    <script crossorigin src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
    <script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>
  </head>
  <body>
    <div id="root"></div>
    <script type="text/babel">
      class GuGuDan extends React.Component {
        constructor(props) {
          super(props);
          this.state = {
            first: Math.ceil(Math.random() * 9),
            second: Math.ceil(Math.random() * 9),
            value: '',
            result: '',
          };
        }
        onSubmit = (e) => {
          e.preventDefault();
          if (parseInt(this.state.value) === this.state.first * this.state.second) {
            this.setState((prevState) => {
              return {
                result: '정답:' + prevState.value,
                first: Math.ceil(Math.random() * 9),
                second: Math.ceil(Math.random() * 9),
                value: '',
              };
            });
            // this.hello.focus();
          } else {
            this.setState({
              result: '땡',
              value: '',
            });
            // this.hello.focus();
          }
        };
        onChange = (e) => {
          this.setState({ value: e.target.value });
        };
        hello;
        render() {
          return (
            <React.Fragment>
              <div>
                {this.state.first}곱하기{this.state.second}는?
              </div>
              <form onSubmit={this.onSubmit}>
                {' '}
                <input
                  //   ref={(c) => {
                  //     this.hello = c;
                  //   }}
                  type="number"
                  value={this.state.value}
                  onChange={this.onChange}
                />
                <button>입력!</button>
              </form>
              <div>{this.state.result}</div>
            </React.Fragment>
          );
        }
      }
    </script>
    <script type="text/babel">
      ReactDOM.render(
        <div>
          <GuGuDan />
          <GuGuDan />
          <GuGuDan />
          <GuGuDan />
        </div>,
        document.querySelector('#root')
      );
    </script>
  </body>
</html>

인프런 커뮤니티 질문&답변