Function compare

compare(
    source?: null | string | number,
    target?: null | string | number,
    nullGreater?: boolean,
): number
Returns 1 if source greater than target, -1 if source less than target, 0 if equals
Parameters
- Optionalsource: null | string | number
  the first comparable
- Optionaltarget: null | string | number
  the second comparable
- nullGreater: boolean = false
  whether a nil (undefined or null) value is considered greater than another non-nil value
Returns number
1 if source greater than target, -1 if source less than target, 0 if equals
Author
David Hsing
Example
```
compare(undefined, null);    // 0
compare(3, undefined, true);    // -1
compare(3, undefined, false);    // 1
compare(3, 2);    // 1
compare(2, 3);    // -1
```