Prefetching in React

prefetch.js

function prefetch(getKey, getValue, getInitialValue, propName) {
  const inFlight = new Set();
  const cache = new Map();
  return ChildComponent => {
    return class extends React.Component {
      state = {value: getInitialValue(this.props)};
      componentWillReceiveProps(nextProps) {
        const key = getKey(nextProps);
        if (cache.has(key)) {
          // Use cached value
          this.setState({value: cache.get(key)});
        }
      }
      async componentWillUpdate(nextProps) {
        const key = getKey(nextProps);
        if (cache.has(key) || inFlight.has(key)) {
          // Request already in-flight
          return;
        }
        inFlight.add(key);
        const value = await getValue(key);
        inFlight.delete(key);
        cache.set(key, value);
        this.setState({value});
      }
      render() {
        const props = {[propName]: this.state.value};
        return <ChildComponent {...props} />;
      }
    };
  };
}

// Can use on multiple components, will share same internal cache
const prefetchThing = prefetch(
  props => props.thingId,
  thingId => fetch(`/api/thing/${thingId}`),
  () => null,
  'thing'
);

function View({thing}) {
  if (user === null) {
    return <LoadingSpinner />;
  }
  return <BlahBlahRealCode thing={thing} />;
}

export default prefetchThing(View);