We can migrate away from having to call str.charAt(num) to being able to do str[num].
This is useful if you wish to check if the first character of a string is a specific character.
There are times when using charAt is preferable. For instance, charAt will return an empty string even if there is index you pass in is out of range, whereas doing str[-1] will return undefined. If the code is always assuming the use of a string, it might be better to use charAt()