增加、减少和总计 JavaScript

Question

I have a beginner predeterminate exercise in React js, but I don´t know how to do it without a "state" when I try set the counter.

Can anyone help me?

 class Counter { constructor() { //initialization of the counter variable this.counter = 0; } increaseOne() { //increase the value in one } decreaseOne() { //decrease the value in one } getValue() { //return the value } } let myNewCounter = new Counter(); myNewCounter.increaseOne(); console.log(myNewCounter.getValue()); myNewCounter.increaseOne(); myNewCounter.increaseOne(); console.log(myNewCounter.getValue()); myNewCounter.decreaseOne(); myNewCounter.decreaseOne(); console.log(myNewCounter.getValue());

My exercise have to show the following:

Answer 1

In vanilla JS you don't have any states built-in. You just change the value of a property.

With the ++ and -- operators you can add or subtract with a value of 1. So in the increaseOne and decreaseOne methods change the value of the this.counter property.

 class Counter { constructor() { this.counter = 0; } increaseOne() { this.counter++; } decreaseOne() { this.counter--; } get value() { return this.counter; } } let myNewCounter = new Counter(); myNewCounter.increaseOne(); console.log(myNewCounter.value); myNewCounter.increaseOne(); myNewCounter.increaseOne(); console.log(myNewCounter.value); myNewCounter.decreaseOne(); myNewCounter.decreaseOne(); console.log(myNewCounter.value);

For the getValue() method you can also use a getter method, which acts like a property but actually returns the result of a function. But this is just a suggestion and should make little difference.