Function appendIfMissing

appendIfMissing(text?, suffix?): string | undefined | null
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 string | undefined | null
a string that concat the given text and suffix
Example
```
appendIfMissing('foo', 'bar');    // 'foobar'
appendIfMissing('foobar', 'bar');    // 'foobar'
```