Wrote this using node 8 to give myself a little refresher. I assume you're using node because you're using file in/out in JavaScript?
Code
var fs = require('fs');
fs.readFile('input.txt', 'utf8', function(err, data) {
if (err) throw err;
var student;
var readingAnswer = false;
var answers = [];
var students = new Map();
data.split('\r\n').forEach(line => {
if (line == '') {
return;
}
if (line.startsWith('Answer Key:')) {
readingAnswer = true;
return;
}
if (line.startsWith('Student')) {
readingAnswer = false;
student = line.replace('Student', '').replace(':' ,'').replace(' ', '');
return;
}
if (readingAnswer) {
answer = line.split(' /');
answers.push(answer);
return;
}
if (student) {
if (students.has(student)) {
students.set(student, students.get(student) + line);
} else {
students.set(student, line);
}
}
});
students.forEach((value, key, map) => {
var score = 0;
var subjects = new Map();
var questions = new Map();
value.split('').forEach((answer, index) => {
var correctAnswer = answers[index][0];
var subjectKey = answers[index][1];
var questionKey = answers[index][2];
var correct = answer == correctAnswer ? 1 : 0;
score += correct;
var subject = subjects.has(subjectKey) ? subjects.get(subjectKey) : { total : 0, correct : 0 };
subject.total++;
subject.correct += correct;
var question = questions.has(questionKey) ? questions.get(questionKey) : { total : 0, correct : 0 };
question.total++;
question.correct += correct;
questions.set(questionKey, question);
subjects.set(subjectKey, subject);
});
var contents = `Student ${key}:\n`;
contents += `Raw Score ${score}/${value.length}\n`;
contents += `\n`;
contents += `Score Breakdown by Subject:\n`;
subjects.forEach((value, key) => {
contents += `${key}: ${value.correct}/${value.total}\n`;
})
contents += `\n`;
contents += `Score Breakdown by Question:\n`;
questions.forEach((value, key) => {
contents += `${key}: ${value.correct}/${value.total}\n`;
})
contents += `\n`;
fs.appendFile('output.txt', contents);
});
});