Found something at https://www.urbanhire.com/careers#full-stack-engineer-urbanhire-1ljj, my attempt to answer

index.js

var zeroPad = function(n) {
    return n > 9 ? '' + n :  '0' + n;
}

var formatDate = function(dt) {
    return "" + dt.getFullYear() + "-" + zeroPad(dt.getMonth() + 1) + "-" + zeroPad(dt.getDate());
}

exports.genDateRange = function(_startDate, _endDate) {
    var startDate = new Date(_startDate);
    var endDate = new Date(_endDate);
    var dateRange = [];
    if (isNaN(startDate.getTime()) || isNaN(endDate.getTime())) {
        return dateRange;
    }
    if (startDate > endDate) {
        var tmpDate = startDate;
        startDate = endDate;
        endDate = tmpDate;
    }
    while (startDate < endDate) {
        dateRange.push(formatDate(startDate));
        startDate.setDate(startDate.getDate() + 1);
    }
    dateRange.push(formatDate(startDate));
    return dateRange;
}

package.json

{
  "name": "urbanhire-date",
  "version": "1.0.0",
  "description": "date range",
  "main": "index.js",
  "scripts": {
    "test": "mocha"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "mocha": "^5.0.1"
  }
}

test.js

var assert = require('assert');
var u = require('./');
describe('Date Range', function() {
    it('should return expected responses', function() {
        var dateRange = u.genDateRange('22 January 2018', '30 January 2018');
        assert.equal(dateRange.length, 9);
        assert.equal(dateRange[0], '2018-01-22');
        assert.equal(dateRange[dateRange.length - 1], '2018-01-30');
    });
});