[Function, Closure, Class] Counter II (closure 함수 여러개 넣기) ⭐️

https://leetcode.com/problems/counter-ii/description/

Counter II - LeetCode

Write a function createCounter. It should accept an initial integer init. It should return an object with three functions.

The three functions are:

• increment() increases the current value by 1 and then returns it.
• decrement() reduces the current value by 1 and then returns it.
• reset() sets the current value to init and then returns it.

 

Example 1:

Input: init = 5, calls = ["increment","reset","decrement"]
Output: [6,5,4]
Explanation:
const counter = createCounter(5);
counter.increment(); // 6
counter.reset(); // 5
counter.decrement(); // 4

Example 2:

Input: init = 0, calls = ["increment","increment","decrement","reset","reset"]
Output: [1,2,1,0,0]
Explanation:
const counter = createCounter(0);
counter.increment(); // 1
counter.increment(); // 2
counter.decrement(); // 1
counter.reset(); // 0
counter.reset(); // 0

 

Constraints:

• -1000 <= init <= 1000
• total calls not to exceed 1000

 

solution

/**
 * @param {integer} init
 * @return { increment: Function, decrement: Function, reset: Function }
 */
var createCounter = function(init) {
    let num = init;
    const initial = init;
    const increment = () => {
        num++;
        return num;
    }
    const decrement = () => {
        num--;
        return num;
    }
    const reset = () => {
        num = initial;
        return num;
    }
    return { increment, decrement, reset };
};

/**
 * const counter = createCounter(5)
 * counter.increment(); // 6
 * counter.reset(); // 5
 * counter.decrement(); // 4
 */

 

solution2

traditional function 사용

var createCounter = function(init) {
  let presentCount = init;

  function increment() {
    return ++presentCount;
  }
  function decrement() {
    return --presentCount;
  }
  function reset() {
    return (presentCount = init);
  }
  return { increment, decrement, reset };
};

 

solution3

arrow function 사용

var createCounter = function(init) {
  let presentCount = init
  return {
    increment: () => ++presentCount,
    decrement: () => --presentCount,
    reset: () => presentCount = init,
  }
};

 

solution4

class 사용

class Counter {
  constructor(init) {
    this.init = init;
    this.presentCount = init;
  }
  increment() {
    this.presentCount += 1;
    return this.presentCount;
  }
  decrement() {
    this.presentCount -= 1;
    return this.presentCount;
  }
  reset() {
    this.presentCount = this.init;
    return this.presentCount;
  }
}

var createCounter = function(init) {
  return new Counter(init);
};