Root of a number - binary search - peer wrote JavaScript code

RootOfNumber_binarySearch.js

function root(x, n) {
  let marginError = 0.001;
  let guess; // upper bound
  
  if(x===1){
    return 1;
  }
  
  if(x>1){
    guess = x;
  }
  
  if(x<1){
    guess = 1;
  }
  
  let increment = x/2;
  
  return tryRoot({x,n,marginError,guess, increment});
}

function tryRoot({x,n,marginError,guess, increment}){
  let cur = 1;
  
  //calculate guess ^ n
  for(let i=0;i<n;i++){
    cur *= guess;
  }
  
  if(x - cur > marginError){
    //increase guess
    let newGuess = guess + increment;
    //retry
    return tryRoot({x,n,marginError,guess:newGuess,increment:increment/2});
  }else if(x - cur < -1 * marginError){
    //lower guess
    let newGuess = guess - increment;
    //retry
    return tryRoot({x,n,marginError,guess: newGuess,increment:increment/2});
  }else{
    //return guess
    return Math.round(guess*1000)/1000;
  }
}