30-seconds-of-code/snippets/Ticker.md

Ticker

Renders a ticker component.

• Use the React.useState() hook to initialize the ticker state variable to 0.
• Define two methods, tick and reset, that will periodically increment timer based on interval and reset interval respectively.
• Return a <div> with two <button> elements, each of which calls tick and reset respectively.

function Ticker(props) {
  const [ticker, setTicker] = React.useState(0);
  let interval = null;

  const tick = () => {
    reset();
    interval = setInterval(() => {
      if (ticker < props.times) setTicker(ticker + 1);
      else clearInterval(interval);
    }, props.interval);
  };

  const reset = () => {
    setTicker(0);
    clearInterval(interval);
  };

  return (
    <div>
      <span style={{ fontSize: 100 }}>{this.state.ticker}</span>
      <button onClick={this.tick}>Tick!</button>
      <button onClick={this.reset}>Reset</button>
    </div>
  );
}

ReactDOM.render(<Ticker times={5} interval={1000} />, document.getElementById('root'));