[Leetcode] JS 30 Counter II

Question

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
• 0 <= calls.length <= 1000
• calls[i] is one of "increment", "decrement" and "reset"

My Solution

/**
 * @param {integer} init
 * @return { increment: Function, decrement: Function, reset: Function }
 */
var createCounter = function(init) {
    var reset = init
    var current = init
    return {
        increment: function() {
            current += 1
            return current
        },
        decrement: function() {
            current -= 1
            return current
        },
        reset: function() {
            current = reset
            return init
        }
    }
};

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

What Can Be Done Better

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

Learning Points

• Arrow Functions: Shorter syntax for function declarations, reducing boilerplate while keeping the same functionality.

• Avoid reset Variable: Directly use init for resetting, since init is already scoped within the closure.
• Inline Return: Simplifies the increment and decrement methods using pre-increment (++) and pre-decrement (--) operators.