Difference of days between two dates in React.JS using moment - reactjs

Question

I made a function which calculates difference between two dates, but i dont know how to take(?) data to it using inputs. I also tried to return diffInDays; and instead of that use this.setState({ diffInDays: diffInDays }). I've tried many combinations but none of them gave me the right result.
calculate(dateFrom, dateTo) {
if (!dateFrom || !dateTo) {
return null;
}
const arrival = moment(dateFrom);
const departure = moment(dateTo);
if (arrival.isAfter(departure)) {
return null;
}
const diffInDays = departure
.endOf('day')
.diff(arrival.startOf('day'), 'days');
return diffInDays;
}
those are the inputs I created:
this one is for the beginning
<div className="form-group">
<label htmlFor="dateFrom">Date From: </label>
<input
type="date"
className="form-control"
id="dateFrom"
onChange={this.onChangeDateFrom}
value={this.state.dateFrom}
name="dateFrom"
/>
</div>
and this one is for the end
<div className="form-group">
<label htmlFor="dateTo">Date to: </label>
<input
type="date"
className="form-control"
id="dateTo"
onChange={this.onChangeDateTo}
value={this.state.dateTo}
name="dateTo"
/>
</div>
and this is the one where I want to see the difference
<div className="form-group">
<label htmlFor="daysDiff">Days Difference: </label>
<input
type="number"
className="form-control"
id="daysDiff"
required
value={this.state.daysDiff}
name="daysDiff"
readOnly
/>
</div>
Picking the dates works fine. They also save in the MongoDB, the problem appears only with the difference of days.

Answer 1

You should use
departure.diff(arrival)
and for getting only day difference
departure.diff(arrival,'days')