tax.js

function INCOME_TAX(input) {
  var taxBrackets = {
    14000: 0.105,
    34000: 0.175,
    22000: 0.30,
    99999: 0.33
  }
  var salary = parseInt(input, 10)
  
  return Object.keys(taxBrackets).reduce(function(acc, taxAmount) {
    var taxPercent = taxBrackets[taxAmount]
    var newTaxableRemaining = acc.taxableIncome - taxAmount
    var limitedAfterTaxAmount = Math.min(taxAmount, acc.taxableIncome)
    
    return {
      taxableIncome: newTaxableRemaining < 0 ? 0 : newTaxableRemaining,
      afterTaxIncome: acc.afterTaxIncome + (limitedAfterTaxAmount - (limitedAfterTaxAmount * taxPercent))
    }
  }, {taxableIncome: salary, afterTaxIncome: 0}).afterTaxIncome
}