2665. Counter II

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# 題目敘述

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

# 解題思路

# Solution

/**

 * @param {integer} init

 * @return { increment: Function, decrement: Function, reset: Function }

 */

var createCounter = function(init) {

    let counter = init;

    const increment = () => counter += 1;

    const decrement = () => counter -= 1;

    const reset = () => counter = init;

    return{increment, decrement, reset};

};

/**

 * const counter = createCounter(5)

 * counter.increment(); // 6

 * counter.reset(); // 5

 * counter.decrement(); // 4

 */

type ReturnObj = {

    increment: () => number,

    decrement: () => number,

    reset: () => number,

}

function createCounter(init: number): ReturnObj {

    let counter: number = init;

    const increment = (): number => counter += 1;

    const decrement = (): number => counter -= 1;

    const reset = (): number => counter = init;

    return {increment, decrement, reset};

};

/**

 * const counter = createCounter(5)

 * counter.increment(); // 6

 * counter.reset(); // 5

 * counter.decrement(); // 4

 */