Day389：实现二进制与十进制的互相转化的两个函数？

[qappleh]

function integerToBin (num) {
  // 64
  const result = []
  while (num / 2) {
    next = num % 2
    num = Math.floor(num / 2)
    result.unshift(next)
  }
  return result
}

function fractionalToBin (num) {
  const result = []
  let i = 0
  while (num !== 0 && i < 54) {
    num = num * 2

    next = num >= 1 ? 1 : 0
    num = num % 1
    i++
    result.push(next)
  }
  return result
}

function decToBinary (num) {
  // 1.5
  const [int, fraction] = String(num).split(/(?=\.)/).map((x, i) => {
    return i === 0 ? integerToBin(x) : fractionalToBin(x)
  })
  return [int, fraction]
}

function binToDec (num) {
  const [_int, _fraction] = String(num).split('.')
  const int = _int.split('').reduceRight((acc, x, i) => {
    return acc + x * 2 ** i
  }, 0)
  const fraction = _fraction ? _fraction.split('').reduce((acc, x, i) => {
    return acc + x * 2 ** -(i + 1)
  }, 0) : 0
  return `${int}${fraction ? '.' + fraction.toString().slice(2) : ''}`
}

console.log(16, integerToBin(16), Number(16).toString(2))
console.log(18, integerToBin(18), Number(18).toString(2))
console.log(0.5, fractionalToBin(0.5), Number(0.5).toString(2))
console.log(0.1, fractionalToBin(0.1), Number(0.1).toString(2))
console.log(1.1, decToBinary(1.1), Number(1.1).toString(2))

console.log(7.875, decToBinary(7.875), Number(7.875).toString(2))
console.log('111.111', binToDec('111.111'), parseInt('111.111', 2))