Lazy Loading Design Pattern in TypeScript

1_Lazy.ts

export class Lazy<T> {
  private _value?: T

  constructor(private initializer: () => T) {
  }

  get value(): T {
    if (this._value == undefined) {
      this._value = this.initializer()
    }
    return this._value
  }

  set value(newValue: T) {
    this._value = newValue
  }
}

2_Usage.ts

import {Lazy} from "....";

const calculated: Lazy<number> = new Lazy(() => power(99, 99)) 
// power function will be called only once, when you access calculated.value at the first time
    
function power(num: number, exp: number) {
  let ans = 1;
  for(let i = 0; i<exp; i++) {
    ans *= num
  }
  console.log(num + " to " + exp + " calculated as " + ans)
  return ans
}
                          
console.log("before first call")                        
console.log(calculated.value)          
console.log(calculated.value)      
console.log(calculated.value)
console.log("after last call")