getLatestWeight().md

Get the most recent weight sample.

On success, the callback function will be provided with a weight object containing the weight value, and the startDate and endDate of the weight sample. Note: startDate and endDate will be the same as weight samples are saved at a specific point in time.

let options = {
  unit: 'pound'
};

AppleHealthKit.getLatestWeight(options, (err: string, results: Object) => {
  if (err) {
    console.log("error getting latest weight: ", err);
    return;
  }
  console.log(results)
});

{
	value: 200,
	startDate: '2016-07-08T12:00:00.000-0400',
	endDate: '2016-07-08T12:00:00.000-0400'
}