priceTicker.js

// MIT

const React = window.React;
const { Component } = React;

const PRICE_URL = 'https://api.etherscan.io/api?module=stats&action=ethprice';
const PRICE_OPTIONS = {
  method: 'GET',
  mode: 'cors',
  headers: {
    'Accept': 'application/json'
  }
};
const PRICE_INTERVAL = 60000;

class PriceTicker extends Component {
  constructor () {
    super();

    const updateTimer = setInterval(() => this.updatePrice(), PRICE_INTERVAL);

    this.state = {
      currentPrice: null,
      updateTimer: updateTimer
    };

    this.updatePrice();
  }
  
  componentWillUnmount () {
    clearInterval(this.state.updateTimer);
  }

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

    if (!currentPrice) {
      return null;
    }

    return React.createElement('div', null, `$${currentPrice}`);
  }

  updatePrice () {
    fetch(PRICE_URL, PRICE_OPTIONS)
      .then((response) => response.json())
      .then(({ result: { ethusd } }) => {
        this.setState({
          currentPrice: parseFloat(ethusd).toFixed(2)
        });
      })
      .catch(() => false);
  }
}

window.parity.extendShell({ type: 'status', component: PriceTicker });