Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

// Generic Stack class
class Stack<T> {
    private items: T[] = [];

push(item: T): void   { this.items.push(item); }
    pop():  T | undefined { return this.items.pop(); }
    peek(): T | undefined { return this.items[this.items.length - 1]; }
    get size(): number    { return this.items.length; }
    isEmpty(): boolean    { return this.items.length === 0; }
}

const numStack = new Stack<number>();
numStack.push(1);
numStack.push(2);
console.log(numStack.peek()); // 2
console.log(numStack.pop());  // 2

// Static members — counter shared across instances
class IdGenerator {
    private static nextId = 1;

static generate(): number {
        return IdGenerator.nextId++;
    }

static reset(): void {
        IdGenerator.nextId = 1;
    }
}

console.log(IdGenerator.generate()); // 1
console.log(IdGenerator.generate()); // 2

// Mixin pattern
type Constructor<T = {}> = new (...args: unknown[]) => T;

function Timestamped<TBase extends Constructor>(Base: TBase) {
    return class extends Base {
        createdAt = new Date();
        updatedAt = new Date();
        touch() { this.updatedAt = new Date(); }
    };
}

class BaseModel { constructor(public id: number) {} }
const TimestampedModel = Timestamped(BaseModel);
const record = new TimestampedModel(1);
console.log(record.createdAt instanceof Date); // true