num2fraction/index.js

'use strict'

var abs = Math.abs
var round = Math.round

function almostEq(a, b) {
  return abs(a - b) <= 9.5367432e-7
}

//最大公约数 Greatest Common Divisor
function GCD(a, b) {
  if (almostEq(b, 0)) return a
  return GCD(b, a % b)
}

function findPrecision(n) {
  var e = 1

  while (!almostEq(round(n * e) / e, n)) {
    e *= 10
  }

  return e
}

function num2fraction(num) {
  if (num === 0 || num === '0') return '0'

  if (typeof num === 'string') {
    num = parseFloat(num)
  }


  var precision = findPrecision(num) //精确度
  var number = num * precision
  var gcd = abs(GCD(number, precision))

  //分子
  var numerator = number / gcd
  //分母
  var denominator = precision / gcd

  //分数
  return round(numerator) + '/' + round(denominator)
}

module.exports = num2fraction