What are the basic types in TypeScript?

// String
let name: string = "John";

// Number
let age: number = 30;

// Boolean
let isActive: boolean = true;

// Null and Undefined
let n: null = null;
let u: undefined = undefined;

// Two ways to declare arrays
let numbers: number[] = [1, 2, 3];
let strings: Array<string> = ["a", "b", "c"];

// Fixed length array with known types
let user: [string, number] = ["John", 30];

// any - opt out of type checking
let data: any = 4;
data = "string"; // OK

// unknown - safer than any
let value: unknown = 10;
if (typeof value === "number") {
  console.log(value + 1); // OK after check
}

// void - no return value
function log(msg: string): void {
  console.log(msg);
}

// never - never returns
function error(msg: string): never {
  throw new Error(msg);
}