React

by ken3desu

HTML

<div id="app"></div>

CSS

body {
  background: #20262E;
  padding: 20px;
  font-family: Helvetica;
}

#app {
  background: #fff;
  border-radius: 4px;
  padding: 20px;
  transition: all 0.2s;
}

li {
  margin: 8px 0;
}

h2 {
  font-weight: bold;
  margin-bottom: 15px;
}

.done {
  color: rgba(0, 0, 0, 0.3);
  text-decoration: line-through;
}

input {
  margin-right: 5px;
}

React

function HasFormStateComponent() {
  // form を state で扱う
  const [formState, setFormState] = React.useState({firstName: '初期値'});
  // 起きた event を元に state を変更する
  const onChange = (event) => setFormState({
    ...formState,
    [event.target.name]: event.target.value
  })

  return (
    <div style={{display: 'flex', flexDirection: 'column' }}>
      <label>名<input type="text" name="firstName" value={formState.firstName} onChange={onChange} /></label>
      <pre>{ JSON.stringify(formState, null, 2) }</pre>
    </div>
  );
}

ReactDOM.render(<HasFormStateComponent />, document.querySelector("#app"))