Lesson 7: Array Methods

Learning Goals

• Use map to transform values.
• Use filter to keep some values.
• Use find to get first matching value.

Example

// Save as lesson7.js
let prices = [8000, 12000, 25000, 6000];

let expensive = prices.filter(function (p) {
  return p >= 10000;
});

let withTax = prices.map(function (p) {
  return p * 1.18;
});

console.log(expensive); // [12000, 25000]
console.log(withTax);   // [9440, 14160, 29500, 7080]

Practice

1. Use filter to keep scores above 50.
2. Use map to add 5 marks to each score.
3. Use find to get first score below 40.

Homework

Given product prices, create one list for cheap items and one list with VAT added.

let productPrices = [3500, 9000, 12000, 5000];

let cheapItems = productPrices.filter(function (p) {
  return p <= 5000;
});

let pricesWithVat = productPrices.map(function (p) {
  return p * 1.18;
});

console.log(cheapItems);
console.log(pricesWithVat);