math.js

function decimal(number) {
  return ({
    toBase: (base) => {
      let remainder = number
      let result = []
      let shouldDivide = true

      while (shouldDivide) {
        result[result.length] = remainder % base
        remainder = Math.floor(remainder / base)

        if (remainder < base) {
          result[result.length] = remainder
          shouldDivide = false
        }
      }

      return result.reverse().join('')
    }
  })
}
  
console.log(decimal(100).toBase(3))