Reads a second degree equation in a string and calculates its root using the Bhaskara formula

calculate-bhaskara.js

function calculateBhaskara (a, b, c) {
  if (a === 0) throw(`the coefficient 'a' cannot be 0 in a second degree equation`)
  
  const delta = calculateDelta (a, b, c)
  const solution = []
  
  if (delta < 0) return solution
  
  const sqrtDelta = Math.sqrt(delta)
  
  solution.push((-b - sqrtDelta) / (2 * a))
  
  if (delta > 0) solution.push((-b + sqrtDelta) / (2 * a))
  
  return solution
}


calculateBhaskara(1, -4, 3) // [ 1, 3 ]

calculateBhaskara(1, -2, 1) // [ 1 ]

calculateBhaskara(1, -2, 2) // [ ]

calculateBhaskara(0, 1, 1) // 'Uncaught the coefficient 'a' cannot be 0 in a second degree equation'

calculate-delta.js

function calculateDelta (a, b, c) {
  return b**2 - 4 * a * c
}

extract-coeficients.js

const splitEntryes = /(?<!\+|\-|^)\+(?!$)|(?<!\+|\-|^)(?=\-(?!$))/g
const matchX = /x/i
const matchXSquared = /x{2}|x\*\*2|x\^2|x²/i
const matchNeutralOperator = /(\+|\-|^)(?=\D)(?!\+|\-|$|\.)/g
const replaceNeutralOperator = '$11'
const matchNumbers = /(?<!\*\*|\^)(\/?\-?[\d.]+)/g

const fixOperations = entry =>
	entry.startsWith('/') ? 1 / Number(entry.slice(1)) : Number(entry)

const reduceValue = (accumulator, currentValue) =>
	accumulator * currentValue

function extractCoeficients (sentence) {
  const entryes = sentence.split(splitEntryes)
  const coeficients = { a: 0, b: 0, c: 0 }
  
  for (let entry of entryes) {
    const value = entry
      .replace(matchNeutralOperator, replaceNeutralOperator)
      .match(matchNumbers)
      .map(fixOperations)
      .reduce(reduceValue)
    
    let key = null
    
    if (entry.match(matchXSquared)) key = 'a'
    else if (entry.match(matchX)) key = 'b'
    else key = 'c'
    
    coeficients[key] += value
  }
  
  return coeficients
}


extractCoeficients('x²-x+1')  // { a: 1, b: -1, c: 1 }

extractCoeficients('x^2+1.5x+3/2')  // { a: 1, b: 1.5, c: 1.5 }

extractCoeficients('x²+xx+x**2+x^2')  // { a: 4, b: 0, c: 0 }