Concatenate the date and time strings and parse them as one, e.g.
var date="23/02/2017";
var time="15:42";
var dateTime = moment(date + ' ' + time, 'DD/MM/YYYY HH:mm');
console.log(dateTime.format('YYYY-MM-DD HH:mm'))<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.17.1/moment.js"></script>