rationalize.js

function rationalize (value) {
  let numerator = 0
  let denominator = 1

  while (value != numerator / denominator) {
    const ratio = numerator / denominator

    if (ratio < value) numerator++
    else if (ratio > value) denominator++
    else break
  }
  
  return [ numerator, denominator ]
}

// rationalize(3.14)
// -> [ 157, 50 ]