2. Type-Annotations

Type annotation can be done by specifying type after a : (colon).

Examples:

let num: number = 20;
 
function addNumbers(a: number, b:number ): number {
	return a + b;
}
 
const addNumbers: number = (a: Number, b: Number) => {
	return a + b;
}

Type-Inference

In typescript, not always have to define a type. It is smart enough to infer the correct type from the provided information.

Example:

const num = 20; // num is inferred as number as the value provided is number type.
 
const store = ["Adesh", 20]; // the type here is inferred as ('string'|'number')[]