moment().duration().days();

npm install moment

const moment = require('moment'); 
  
let durationOne = moment.duration(28, 'days'); 
let durationTwo = moment.duration(35, 'days'); 
  
// This returns 28 as the number of 
// days is less than a whole day 
console.log( 
    "durationOne days is:", durationOne.days() 
) 
  
// This returns 4 as the number of days 
// is greater than a whole month 
console.log( 
    "durationTwo days is:", durationTwo.days() 
)

durationOne days is: 28
durationTwo days is: 4

const moment = require('moment'); 
  
let durationA = moment.duration(100, 'hours'); 
let durationB = moment.duration(1550, 'hours'); 
  
// The asdays() method will return the 
// length of the duration in days 
console.log( 
    "Length of durationA in days is:", durationA.asDays() 
) 
  
// This will return 4 as the number of complete days 
console.log("durationA days is:", durationA.days()) 
  
console.log( 
    "Length of durationB in days is:", durationB.asDays() 
) 
  
// This will return 3, as the 2 months  
// (or 61 days are considered) and 3 days 
// remain of the new month 
console.log("durationB days is:", durationB.days())

Length of durationA in days is: 4.166666666666667
durationA days is: 4
Length of durationB in days is: 64.58333333333333
durationB days is: 3