04_deep_foundations_function_scope_arrow_resolved.js

var getStudentFromId = studentId => studentRecords.find(record => record.id == studentId);

var printRecords = recordIds =>
  recordIds.map(getStudentFromId)
    .sort(
      (record1,record2) => record1.name < record2.name ? -1 : record1.name > record2.name ? 1 : 0
    )
    .forEach(record =>
      console.log(`${record.name} (${record.id}): ${record.paid ? "Paid" : "Not Paid"}`)
    );

var paidStudentsToEnroll = () =>
  [ ...currentEnrollment,
    ...(
      studentRecords.filter(record => (record.paid && !currentEnrollment.includes(record.id)))
      .map(record => record.id)
    )
  ];

var remindUnpaid = recordIds =>
  printRecords(
    recordIds.filter(studentId => !getStudentFromId(studentId).paid)
  );


// ********************************

var currentEnrollment = [ 410, 105, 664, 375 ];

var studentRecords = [
  { id: 313, name: "Frank", paid: true, },
  { id: 410, name: "Suzy", paid: true, },
  { id: 709, name: "Brian", paid: false, },
  { id: 105, name: "Henry", paid: false, },
  { id: 502, name: "Mary", paid: true, },
  { id: 664, name: "Bob", paid: false, },
  { id: 250, name: "Peter", paid: true, },
  { id: 375, name: "Sarah", paid: true, },
  { id: 867, name: "Greg", paid: false, },
];

printRecords(currentEnrollment);
console.log("----");
currentEnrollment = paidStudentsToEnroll();
printRecords(currentEnrollment);
console.log("----");
remindUnpaid(currentEnrollment);

/*
  Bob (664): Not Paid
  Henry (105): Not Paid
  Sarah (375): Paid
  Suzy (410): Paid
  ----
  Bob (664): Not Paid
  Frank (313): Paid
  Henry (105): Not Paid
  Mary (502): Paid
  Peter (250): Paid
  Sarah (375): Paid
  Suzy (410): Paid
  ----
  Bob (664): Not Paid
  Henry (105): Not Paid
  */