Magnetometer error

[sareh88]

i am facing this error:
TypeError: undefined is not an object evaluation
mSensorManager.startMagnetometer
here is mt code :
var mSensorManager = require('NativeModules').SensorManager;

componentDidMount() {
mSensorManager.startMagnetometer(100);
DeviceEventEmitter.addListener('azimuthChanged', this.azimuthChanged.bind(this));

   this.interval = setInterval(() => {
  this.setState({
    azimuth: this.currentAzimuth
  });
}, 100);

}