TypeScript Date

// 1. No arguments: captures the current date and time
const now: Date = new Date();

// 2. Unix timestamp (number): milliseconds since the Epoch
const fromEpoch: Date = new Date(1672531200000);

// 3. Date string (string): parsed internally via Date.parse()
const fromString: Date = new Date("2023-01-01T00:00:00Z");

// 4. Component values (numbers): year, month (0-indexed), date, hours, minutes, seconds, ms
const fromComponents: Date = new Date(2023, 0, 1, 0, 0, 0, 0);

// Returns the current timestamp in milliseconds
const currentMs: number = Date.now();

// Parses a valid ISO 8601 date string into a timestamp
const parsedMs: number = Date.parse("2023-01-01T12:00:00Z");

// Returns a timestamp from UTC component values
const utcMs: number = Date.UTC(2023, 0, 1);

const dt: Date = new Date();

// Getters return numbers
const year: number = dt.getFullYear();       // e.g., 2023
const month: number = dt.getMonth();         // 0-11
const day: number = dt.getDay();             // 0-6 (0 = Sunday)
const utcHours: number = dt.getUTCHours();   // 0-23

// Setters mutate the instance and return the new timestamp (number)
const newTimestamp: number = dt.setFullYear(2024);

const dt: Date = new Date();

// ISO 8601 string format (YYYY-MM-DDTHH:mm:ss.sssZ)
const iso: string = dt.toISOString();

// Primitive value (timestamp in milliseconds)
const ms: number = dt.getTime();
const valueOf: number = dt.valueOf();

// Locale-specific formatting
const localeDate: string = dt.toLocaleDateString();
const localeTime: string = dt.toLocaleTimeString();

const input: unknown = new Date("invalid-string");

// 1. Type narrowing via instanceof
if (input instanceof Date) {
    // TypeScript now recognizes 'input' as a Date object
    
    // 2. Validating the internal timestamp
    // An invalid date returns NaN for getTime()
    const isValid: boolean = !isNaN(input.getTime());
    
    if (isValid) {
        console.log(input.toISOString());
    }
}