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counter.js

class Counter extends React.Component {
  constructor(props) {
    super(props);

    this.state = {
      count: props.count || 0
    };

    this.updateCount = this.updateCount.bind(this);
  }

  updateCount(increment) {
    const { count } = this.state;

    if (increment) {
      this.setState({
        count: count + 1
      });
    } else {
      this.setState({
        count: count - 1
      });
    }
  }

  render() {
    const { count } = this.state;

    return React.createElement(
      "div",
      null,
      React.createElement("p", null, "The current count is ", count),
      React.createElement(
        "button",
        {
          type: "button",
          onClick: () => {
            return this.updateCount(true);
          }
        },
        "Increment"
      ),
      React.createElement(
        "button",
        {
          type: "button",
          onClick: () => {
            return this.updateCount(false);
          }
        },
        "Decrement"
      )
    );
  }
}

export default Counter;