The substring method returns a string containing the substring from start up to, but not including, end.
The substring method uses the lower value of start and end as the beginning point of the substring. For example, strvar.substring(0, 3) and strvar.substring(3, 0) return the same substring.
If either start or end is NaN or negative, it is replaced with zero.
The length of the substring is equal to the absolute value of the difference between start and end. For example, the length of the substring returned in strvar.substring(0, 3) and strvar.substring(3, 0) is three.