TypeScript Syntax and Data Types: An In-depth Guide

Variable Declaration

To declare variables in TypeScript, we use the let or const keywords.

For example: let num: number = 10; or const message: string = "Hello";


Primitive Data Types

TypeScript supports primitive data types such as number, string, boolean, null, and undefined.

For example: let age: number = 25;, let name: string = "John";, let isActive: boolean = true;



To declare an array in TypeScript, we use the type[] syntax or Array<type>.

For example: let numbers: number[] = [1, 2, 3, 4, 5]; or let names: Array<string> = ["John", "Jane", "Alice"];



To define the data type for an object, we use the {} syntax and specify the type of each property inside it.

For example:

let person: { 
  name: string; 
  age: number; 
  isEmployed: boolean; 
} = {
  name: "John",
  age: 25,
  isEmployed: true



TypeScript allows us to define the data type for functions.

For example:

function add(a: number, b: number): number {
  return a + b;


These are some examples of the basic syntax of TypeScript and the supported data types, including primitive types, arrays, objects, and functions.

TypeScript provides the ability to extend syntax and supports more complex data types to fit your application development needs.