Free Typescript Classroom Course

In the previous class, we set up our development environment and delved into Typescript's Primitive Types.

In today's class, we will learn how to work with Objects and Arrays in Typescript.

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Introduction

In this class, we will learn about Objects and Arrays in Typescript. Let's explore different ways in which we can create objects and arrays in our projects with Typescript.

Literal Objects

One of the simplest ways to create an object is through object literals. This approach is particularly useful when you already have prior knowledge of the object's properties, as you cannot add new properties later.

const objeto = {
  chaveA: 'value',
  chaveB: 'value',
};

objeto.chaveC = 'value';

Index Signature

One way to create dynamic objects is using Index Signature. This approach is especially useful when we don't know in advance what the object's properties will be.

const objeto: { [key: string]: string } = {
  chaveA: 'value A',
  chaveB: 'value B',
};

objeto.chaveC = 'value C';

console.log(objeto);

Record

Another way we can create dynamic objects in Typescript is using Record. Record is one of the Utility Types in the Typescript toolbox. Let's explore more about Utility Types later. For now, what you need to know is that when using Record, we need to specify the type for the key and the value of the object between <>.

const objeto: Record<string, string> = {
  chaveA: 'value A',
  chaveB: 'value B',
};

Array Literals

The simplest way to create an array is using a literal array, which is a comma-separated list of elements enclosed in square brackets.

const arrayDeNumeros: number[] = [1, 2, 3];
const arrayDeString: string[] = ['Josh', 'Patrick', 'Lamar'];
const arrayDeStringENumeros: (string | number)[] = [1, 'Alice', 55];

console.log(arrayDeString);
console.log(arrayDeNumeros);
console.log(arrayDeStringENumeros);

Array Constructor

You can also use the Array constructor to create a new array.

const arrayDeNumeros: Array<number> = [1, 2, 3];
const arrayDeString: Array<string> = ['Josh', 'Patrick', 'Lamar'];
const arrayDeStringENumeros: Array<string | number> = [1, 'Alice', 55];

console.log(arrayDeString);
console.log(arrayDeNumeros);
console.log(arrayDeStringENumeros);

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You can access the class code by accessing the link below:
https://github.com/d3vlopes/curso-typescript/tree/aula-002

Next class

In the next class, we will explore functions in Typescript. Let's learn how to define parameter types, return types and more!

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