Declarative methods on array data collection

data.js

const students = [
  {
    name: 'Oliver Mensah',
    email: 'olie@gmail.com',
  },
  {
    name: 'Olivia Mansah',
    email: 'oliia@gmail.com',
  },
];

//Declarative
const emails = students.map((student) => student.email);
// console.log(emails);

//filter
const oliviaData = students.filter(
  (student) => student.name === 'Olivia Mansah'
);
// console.log(oliviaData);

//reduce
const combinedEmails = students.reduce(
  (acc, student) => acc + student.email,
  ''
);
console.log(combinedEmails);

//creating declarative methods
//imp map
function impMap(data) {
  const studentEmails = [];
  for (student of students) {
    studentEmails.push(student.email);
  }
  return studentEmails;
}
console.log(impMap(students));

function impFilter(data) {
  const oliviaData = [];
  for (student of students) {
    if (student.name === 'Olivia Mansah') {
      oliviaData.push(student);
    }
  }
  return oliviaData;
}
console.log(impFilter(students));

function impReduce(data) {
  let combinedEmails = '';
  for (student of students) {
    combinedEmails += student.email;
  }
  return combinedEmails;
}

console.log(impReduce(students));

function map(data, func) {
  const result = [];
  for (el of data) {
    result.push(func(el));
  }
  return result;
}
studentEmails = map(students, (student) => student.email);

console.log(studentEmails);

function filter(data, func) {
  const result = [];
  for (el of data) {
    if (func(el)) result.push(el);
  }
  return result;
}

console.log(filter(students, (student) => student.name === 'Olivia Mansah'));

function reduce(data, func, initialValue) {
  let acc = initialValue;
  for (el of data) {
    acc = func(acc, el);
  }
  return acc;
}

console.log(reduce(students, (acc, student) => acc + student.email, ''));

const shoppingCart = [
  { product: 'Banana', unit_price: 79, quantity: 3 },
  { product: 'Milk', unit_price: 499, quantity: 1 },
  { product: 'Cream', unit_price: 599, quantity: 2 },
  { product: 'Sugar', unit_price: 249, quantity: 1 },
  { product: 'Apple', unit_price: 76, quantity: 6 },
  { product: 'Bread', unit_price: 229, quantity: 2 },
];

/*
 * Write a collection pipeline that calculates the total price of
 * all the items in this shopping cart.
 *
 * Do not use any loops, if statements, or ternary operators.
 *
 * Good luck!
 *
 * $totalPrice = $shoppingCart....
 */

const sum = shoppingCart.reduce(
  (acc, item) => acc + item.unit_price * item.quantity,
  0
);
console.log(sum);

const employees = [
  {
    name: 'John',
    email: 'john3@example.com',
    sales: [
      { customer: 'The Blue Rabbit Company', order_total: 7444 },
      { customer: 'Black Melon', order_total: 1445 },
      { customer: 'Yellow Cake', order_total: 700 },
    ],
  },
  {
    name: 'Jane',
    email: 'jane8@example.com',
    sales: [
      { customer: 'The Grey Apple Company', order_total: 203 },
      { customer: 'Yellow Cake', order_total: 8730 },
      { customer: 'The Blue Rabbit Company', order_total: 3337 },
      { customer: 'Green Mobile', order_total: 5310 },
    ],
  },
  {
    name: 'Dave',
    email: 'dave1@example.com',
    sales: [
      { customer: 'The Acute Toaster Company', order_total: 1091 },
      { customer: 'Green Mobile', order_total: 2370 },
    ],
  },
  {
    name: 'Dana',
    email: 'dana2@example.com',
    sales: [
      { customer: 'Green Mobile', order_total: 203 },
      { customer: 'Yellow Cake', order_total: 8730 },
      { customer: 'The Piping Bull Company', order_total: 3337 },
      { customer: 'The Cloudy Dog Company', order_total: 5310 },
    ],
  },
  {
    name: 'Beth',
    email: 'beth9@example.com',
    sales: [
      { customer: 'The Grey Apple Company', order_total: 1091 },
      { customer: 'Green Mobile', order_total: 2370 },
    ],
  },
];

/* 
  Write a collection pipeline  to find the customer whose combined
 * total order value is the highest.
 *
 * Do not use any loops, if statements, or ternary operators.
 *
 * Good luck!
 *
 * mostValuableCustomer = employees->...
 */

max = employees
  .reduce(function (acc, cur) {
    return [...acc, ...cur['sales']];
  }, [])
  .reduce(function (prev, current) {
    return prev['order_total'] > current['order_total'] ? prev : current;
  });
console.log(max['customer']);

//PHP 
 $employees
            ->pluck('sales')
            ->flatten(1)
            ->groupBy('customer')
            ->map(function ($groupedSales, $customer) {
                return $groupedSales->sum('order_total');
            })
            ->sort()
            ->reverse()
            ->keys()
            ->first();