Newtons Root Method (Not) Implemented In Js.

newton.js

var derivativeOfATerm = function(arr) {
  var one = arr[0];
  var two = arr[1];
  var derivative = [];
  if(two <= 0) {
    return [0,0];
  } else {
    derivative.push(one*two);
    derivative.push(two-1);
    return derivative;
  }
};

var derivativeOfPolynomial = function(arr, order = 1) {
  var derivative = [];
  for(var i = 0; i < arr.length; i++) {
    //console.log(arr[i]);
    derivative.push(derivativeOfATerm(arr[i]));
  }
  if(order === 1) {
    return derivative;
  } else {
    return derivativeOfPolynomial(derivative, order-1);
  }
};

var runPolynomial = function(poly, num) {
  var array = [];
  for(var i = 0; i < poly.length; i++) {
    array.push(Math.pow(num,poly[i][1])*poly[i][0]);
  }
  return array.reduce((a,b) => a+b);
};

var newtonRootFind = function(polynomial, guess, limit = 10) {
  var derivative = derivativeOfPolynomial(polynomial);
  var previous = guess;
  var next;
  for(var i = 0; i < limit; i++) {
    next = previous - (runPolynomial(polynomial,previous))/(runPolynomial(derivative,previous));
    previous = next;
  }
  return previous;
};