Review: Objects and Collections
Review key concepts from object shapes, type aliases, arrays, tuples, and immutability, and see how they all work together to model complex, reliable data in TypeScript.
Let’s zoom out.
This chapter was about shaping the world: defining what our data is, what it isn’t, and how it’s allowed to behave. We’ve moved beyond casual JavaScript objects into a world of contracts, constraints, and clarity.
We’ve learned to model structure, enforce it, freeze it, and name it. And now, we’re going to connect the dots.
Define object shape early to prevent bugs
JavaScript lets us create objects on a whim. But with great freedom comes great fragility. Did you miss a property? Mistyped a key? The runtime won’t warn us—it may simply fail during execution.
That’s why we learned to type object shapes.
const user: { name: string; age: number } = {name: "Alice",age: 30,};
When we declare an object with an ...