Function randomString

randomString(
    minLength?: number,
    maxLength?: number,
    characters?: string,
): undefined | string
Returns a random string that between the length range
Parameters
- OptionalminLength: number
  the min length, inclusive
- OptionalmaxLength: number
  the max length, exclusive
- characters: string = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
  the source characters to be generated from
Returns undefined | string
a random string that between the length range
Author
David Hsing
Example
```
randomString(8);
```