genericClass.ts

interface GenericInterface<U> {
  value: U
  getIdentity: () => U
}

class IdentityClass<T> implements GenericInterface<T> {
  value: T

  constructor(value: T) {
    this.value = value
  }

  getIdentity () : T {
    return this.value
  }

}

const myNumberClass = new IdentityClass<Number>(1)
console.log(myNumberClass.getIdentity()) // 1

const myStringClass = new IdentityClass<string>("Hello!")
console.log(myStringClass.getIdentity()) // Hello!