Let’s take a very basic use case of the useState() hook; updating the count variable on each click. The code look perfectly fine and will work as expected in almost every time. BUT the issue with this code is that setCount() doesn’t guarantee that the previous count that it’s going to use to either increment and decrement to get the next state will be the latest one. To make sure that we always use the latest previous state for calculating the new state, we need to pass a callback function in the setCount rather than directly doing computation inside it.
Array includes() method The old way to check if some value is present inside an array was to use Array’s indexOf() method. IndexOf() returned -1 if element is not found or else the position of element if it’s present in the array. Exponential operator Similar to Math.pow(), the exponential operator ** was introduced in ES2016. It returns the first argument raised to the power of second argument.