Grading function for ANC schemas

grade.js

function GRADE(los, plos = null, prevGrade = null) {
  if (prevGrade && prevGrade == 'P') {
    return 'P';
  }

  if (los.length > 1) {
    throw 'Invalid range for LOs'
  }

  los = los[0];

  if (plos != null) {
    if (plos.length > 1) {
      throw 'Invalid range for previous LOs'
    }
    
    plos = plos[0];
  }

  passResult = Array(los.length).fill('A');

  actualResult = passResult.map((e,i) => e === los[i] ? 1 : 0);

  secondAttempt = false;

  if (Array.isArray(plos)) {
    secondAttempt = true;

    actualResult = actualResult.map((e,i) => {
      if (e == 1) {
        return 1;
      }
      return passResult[i] === plos[i] ? 1 : 0;
    });
  }      
  
  aggregatedResult = actualResult.reduce((a, c) => a & c);

  if (aggregatedResult === 1) {
    return 'P';
  }
  
  if (secondAttempt) {
    return 'F/R';
  }
  
  return 'R';
}