compare data properties

comparator.js

function comparator(data: Object, nextData: Object): Object {
  return {
    changedFrom(key: string, actual: 'string', prev: string): boolean {
      return data[key] === prev && nextData[key] === actual;
    },
    changedTo(key: string, actual: 'string'): boolean {
      return data[key] !== actual && nextData[key] === actual;
    },
    changed(key: string): boolean {
      return data[key] !== nextData[key];
    },
    increased(key: string): boolean {
      return data[key] < nextData[key];
    },
    decreased(key: string): boolean {
      return data[key] > nextData[key];
    },
  };
}

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