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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

# Solution

/**
 * @param {integer} init
 * @return { increment: Function, decrement: Function, reset: Function }
 */
var createCounter = function(init) {
    let tmp = init;
    increment = () => ++tmp;
    decrement = () => --tmp;
    reset = () => tmp = 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 tmp: number = init;
    const increment = (): number => ++tmp;
    const decrement = () => --tmp;
    const reset = (): number => tmp = init;
    return {increment, decrement, reset};
};
/**
 * const counter = createCounter(5)
 * counter.increment(); // 6
 * counter.reset(); // 5
 * counter.decrement(); // 4
 */