Free course · Lesson 3 of 5

Arrays & Objects

In this lesson you will

Store data in arrays and objects
Use array methods such as map and filter

Arrays hold ordered lists of values; objects hold labeled data as key-value pairs — JavaScript's equivalent of a Python dict or a Java HashMap. Together they can represent almost any real-world data.

const students = ["Amina", "Deng", "Grace"]; — a simple array.
const student = { name: "Amina", level: "Beginner", score: 78 }; — an object.
Destructuring: const { name, score } = student; pulls fields out directly.
JSON.stringify() and JSON.parse() convert between objects and text — essential for APIs.

💡 Practical Skill: Model real records as an array of objects — this is exactly the shape of data returned by most web APIs as JSON.

Worked exampleFiltering Student Records

JavaScript

const students = [  { name: "Amina", level: "Beginner", score: 78 },  { name: "Deng", level: "Intermediate", score: 91 },  { name: "Grace", level: "Beginner", score: 64 },]; const passed = students  .filter((s) => s.score >= 70)  .map((s) => s.name); console.log("Passed:", passed); const levelsOffered = [...new Set(students.map((s) => s.level))];console.log("Levels in this class:", levelsOffered);

Practice exercise

Create an array of product objects with names and prices, then use filter to list the products under 5,000 SSP.

Key takeaways

Real data is usually an array of objects
map transforms, filter selects and reduce combines
Array methods return new arrays and leave the original unchanged

In the full program Module 3: Arrays, Objects and Array Methods See how this topic is taught in depth, with practical activities and an assessment.

Free self-study lesson — no certificate. For the full instructor-led program, see registration options.