Moment fromNow methods. Minimalist implementation.

fromNow.js

/**
 * Lucas Nogueira Munhoz
 * Start: 08:40AM - End: 10:03AM
 */

// units.js
const units = { second: 1000 };
units.minute = 60 * units.second;
units.hour = 60 * units.minute;
units.day = 24 * units.hour;
units.week = 7 * units.day;
units.month = 4 * units.week;
units.year = 12 * units.month

// units_range.js
const unitsRange = { 
  second: {
    min: units.second, 
    max: units.second * 59
  }
}
unitsRange.minute = {
  min: units.minute, 
  max: units.minute * 59 + unitsRange.second.max
}
unitsRange.hour = {
  min: units.hour, 
  max: units.hour * 23 + unitsRange.minute.max
}
unitsRange.day = {
  min: units.day, 
  max: units.day * 6 + unitsRange.hour.max
}
unitsRange.week = {
  min: units.week, 
  max: units.week * 3 + unitsRange.day.max
}
unitsRange.month = {
  min: units.month,
  max: units.month * 11 + unitsRange.week.max
}

// fromNow.js
const toHumanTime = (timestamp, unit) => {
  return Math.floor(timestamp / unit);
}

const toHumanString = (time, unit) => {
 const humanTime = toHumanTime(time, units[unit])
 return humanTime === 1
 ? `${humanTime} ${unit} ago`
 : `${humanTime} ${unit}s ago`
}

const fromNow = timestamp => {
  const time = new Date().getTime() - new Date(timestamp).getTime()
  
  for (var unit in unitsRange) {        
    if (time < units.second) return 'now';
    if (unitsRange[unit].min <= time && unitsRange[unit].max >= time ) {
       return toHumanString(time, unit);
    }
  }
  return toHumanString(time, 'year')
}

// --------------------------------------------
// ------- Testes -----------------------------
// --------------------------------------------

// menos de 1 segundo atrás
console.log(fromNow(new Date().getTime()))
            
// 1 segundo atrás
console.log(fromNow(new Date().getTime() - units.second))

// 23 segundos atrás
console.log(fromNow(new Date().getTime() - units.second * 23))

// 1 minuto atrás
console.log(fromNow(new Date().getTime() - units.minute))

// 54 minutos atrás
console.log(fromNow(new Date().getTime() - units.minute * 54))

// 1 dia atrás
console.log(fromNow(new Date().getTime() - units.day))

// 6 dias atrás
console.log(fromNow(new Date().getTime() - units.day * 6))

// 2 semanas atrás
console.log(fromNow(new Date().getTime() - units.week * 2))

// 3 meses atrás
console.log(fromNow(new Date().getTime() - units.month * 3))

// 4 anos atrás
console.log(fromNow(new Date().getTime() - units.year * 4))