Function appendIfMissing

appendIfMissing(
text?: null | string,
suffix?: null | string,
): undefined | null | string
Returns a string that concat the given text and suffix
Parameters
- Optionaltext: null | string
  the text to check
- Optionalsuffix: null | string
  the suffix to append
Returns undefined | null | string
a string that concat the given text and suffix
Author
David Hsing
Example
```
appendIfMissing('foo', 'bar');    // 'foobar'
appendIfMissing('foobar', 'bar');    // 'foobar'
```