index.js

'use strict';
import {NativeEventEmitter, NativeModules} from 'react-native';

const {RNAttitude} = NativeModules;
const AttitudeEventEmitter = new NativeEventEmitter(RNAttitude);
let attitudeSubscriptions = [];
let attitudeUpdatesEnabled = false;

const Attitude = {

  // Starts watching/observing of attitude
  // The success function is called upon every change
  watch: function(success) {
    if (!attitudeUpdatesEnabled) {
      RNAttitude.startObserving();
      attitudeUpdatesEnabled = true;
    }
    const watchID = attitudeSubscriptions.length;
    attitudeSubscriptions.push(AttitudeEventEmitter.addListener('attitudeUpdate', success));
    return watchID;
  },

  // Stops all watching/observing of the passed in watch ID
  clearWatch: function(watchID) {
    const sub = attitudeSubscriptions[watchID];
    if (!sub) {
      // Silently exit when the watchID is invalid or already cleared
      return;
    }
    sub.remove(); // removes the listener
    attitudeSubscriptions[watchID] = undefined;
    // check for any remaining watchers
    let noWatchers = true;
    for (let ii = 0; ii < attitudeSubscriptions.length; ii++) {
      if (attitudeSubscriptions[ii]) {
        noWatchers = false; // still valid watchers
      }
    }
    if (noWatchers) {
      RNAttitude.stopObserving();
      attitudeUpdatesEnabled = false;
    }
  },

  // Stop all watching/observing
  stopObserving: function() {
    let ii = 0;
    RNAttitude.stopObserving();
    for (ii = 0; ii < attitudeSubscriptions.length; ii++) {
      const sub = attitudeSubscriptions[ii];
      if (sub) {
        sub.remove();
      }
    }
    attitudeSubscriptions = [];
    attitudeUpdatesEnabled = false;
  },

  // Zeros the baseline attitude based on our current attitude
  zero: function() {
    RNAttitude.zero();
  },

  // Resets the attitude reference
  reset: function() {
    RNAttitude.reset();
  },

  // Indicates if barometer updates are available on this device
  isSupported: async function() {
    return await RNAttitude.isSupported();
  },

  // Sets the desired output to either 'heading', 'attitude' or 'both'
  setOutput: function(output) {
    RNAttitude.setOutput(output);
  },

  // Sets the interval between event samples
  setInterval: function(interval) {
    RNAttitude.setInterval(interval);
  },

  // Sets the device rotation to either 'none', 'left' or 'right'
  setRotation: function(rotation) {
    RNAttitude.setRotation(rotation);
  }

};

export default Attitude;