Typescript Variables

Typescript variables

Created By: chatGPT

In TypeScript, variables can be declared using let, const, or var. Each has its own use case and scope rules. let and const are preferred in modern TypeScript for variable declarations due to their block scope.

let name: string = 'John';
const age: number = 30;
var isActive: boolean = true;

Using let allows you to reassign the variable later, while const creates an immutable reference to the variable. If you need to change the value, you will need to use let instead.

let score: number = 10;
score = 20;  // This is valid

const pi: number = 3.14;
pi = 3.15;  // This will cause an error

You can also declare multiple variables in a single line, which can help in initializing them efficiently. Additionally, you can declare a variable without assigning a value. In this case, it will have the type undefined until it's assigned.

let x: number, y: string;
x = 5;
y = 'Hello';

let z: boolean;
// z is currently undefined

TypeScript supports type annotations, allowing you to specify the type of a variable explicitly. This helps in catching errors at compile time. You can annotate basic types as well as complex types like arrays or objects.

let numbers: number[] = [1, 2, 3];
let person: { name: string; age: number; } = { name: 'Jane', age: 25 };

When working with dynamic types, you can use the any type to tell TypeScript that the variable can hold any data type. However, this should be used sparingly as it can lead to less type safety.

let data: any;
data = 'Hello';
data = 100; // Still valid