Shinchan, Masaochan, Kazamachan walk into a pizza shop. The menu only has six options. They have a specific condition to be sufficed before making a purchase. Condition of Shinchan

• No Capsicum

Condition of Kazama

• Must include cheese.

Collective Condition

• The total should be below 1000.

Let's understand the array of methods with the processes they used to make a purchase.

Step 1

The shop provides taste before you buy. They demand to taste samples. The shopkeeper maps through all five pizzas and gives a slice of them.

const menu = ["pizza 1", "pizza 2", "pizza 3", "pizza 4", "pizza 5", "pizza 6"];
const tastesamples = menu.map(item => `A slice of ${item}`);
console.log(menu);
console.log(tastesamples);
/*
['pizza 1', 'pizza 2', 'pizza 3', 'pizza 4', 'pizza 5', 'pizza 6']
[
  'A slice of pizza 1',
  'A slice of pizza 2',
  'A slice of pizza 3',
  'A slice of pizza 4',
  'A slice of pizza 5',
  'A slice of pizza 6'
]
*/

Step 2

Now Shinchan and Kazama will filter out the options that don't meet their condition.

const menu = [
  {
    id: 1,
    name: "pizza 1",
    price: 258,
    ingredients: ["cheese", "tomato", "jalapeno"],
  },
  {
    id: 2,
    name: "pizza 2",
    price: 208,
    ingredients: ["cheese", "tomato", "jalapeno"],
  },
  {
    id: 3,
    name: "pizza 3",
    price: 298,
    ingredients: ["capsicum", "cheese", "tomato", "mushroom"],
  },
  {
    id: 4,
    name: "pizza 4",
    price: 529,
    ingredients: ["tomato", "cheese"],
  },
  {
    id: 5,
    name: "pizza 5",
    price: 568,
    ingredients: ["baby corn", "egg", "basil"],
  },
  {
    id: 6,
    name: "pizza 6",
    price: 568,
    ingredients: ["baby corn", "egg", "basil", "mushroom", "tomato"],
  },
];

Shinchan's condition

const shinsarray = menu.filter(item => !item.ingredients.includes("capsicum"));
console.log(shinsarray);

Kazama's condition

const kazarray = shinsarray.filter(item => item.ingredients.includes("cheese"));
console.log(kazarray);

Step 3 Now let's write a pure function to check if our order fits our budget.

function isbudgetfriendly(array) {
  const total = array.reduce((acc, item) => acc + item.price, 0);
  if (total < 1000) console.log(true);
  else console.log(false);
}
console.log(isbudgetfriendly(kazarray)); // true

Since our order is budget-friendly we can go ahead with it.

Quick summary

• Map function maps through the array.
• While this mapping goes on, we can operate the elements mapped.
• The operation performed on the elements is passed as a callback function.
• The filter function takes a callback function as an argument.
• This function checks if each element sufficed specified condition.
• If the outcome is true, the element passes.
• The reduce function takes a callback with two parameters a) Accumulator b) Current item.
• We can operate the current item and also store the outcomes from the previous ones in the accumulator.
• It has predominant use in going from many to one.