Moment.js does not provide a way to set the time of an existing moment through a string. Why not just concatenate the two:
var date = "2017-03-13";
var time = "18:00";
var timeAndDate = moment(date + ' ' + time);
console.log(timeAndDate);
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Alternatively, you can use two Moment objects and use the getters and setters. Although a far more verbose option, it could be useful if you can't use concatenation:
let dateStr = '2017-03-13',
timeStr = '18:00',
date = moment(dateStr),
time = moment(timeStr, 'HH:mm');
date.set({
hour: time.get('hour'),
minute: time.get('minute'),
second: time.get('second')
});
console.log(date);
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