Mailspring/app/internal_packages/composer/lib/subject-text-field.jsx

import React, { Component } from 'react';
import PropTypes from 'prop-types';

export default class SubjectTextField extends Component {
  static displayName = 'SubjectTextField';

  static containerRequired = false;

  static propTypes = {
    value: PropTypes.string,
    onSubjectChange: PropTypes.func,
  };

  onInputChange = ({ target: { value } }) => {
    this.props.onSubjectChange(value);
  };

  focus() {
    this._el.focus();
  }

  render() {
    const { value } = this.props;

    return (
      <div className="composer-subject subject-field">
        <input
          ref={el => {
            this._el = el;
          }}
          type="text"
          name="subject"
          placeholder="Subject"
          value={value}
          onChange={this.onInputChange}
        />
      </div>
    );
  }
}