Function extractExtension

extractExtension(
    imageSource?: string | null,
    allowedExtensions?: (string | null | undefined)[],
    fallback?: string,
): string
Extracts the file extension from an image source (URL or local file path) and returns it if allowed, otherwise returns the fallback
Parameters
- OptionalimageSource: string | null
  The image URL or local file path to extract the extension from
- allowedExtensions: (string | null | undefined)[] = DEFAULT_EXTENSIONS
  The list of allowed extensions (with leading dot, e.g. ['.jpg', '.png']). Defaults to ['.jpg', '.jpeg', '.png', '.gif', '.webp', '.bmp', '.heic', '.heif']
- fallback: string = '.jpg'
  The fallback extension with leading dot (defaults to '.jpg')
Returns string
the extracted extension if allowed, otherwise the fallback extension
Author
David Hsing
Example
```
extractExtension('https://example.com/image.png');    // '.png'
extractExtension('http://example.com/image.webp?size=200');   // '.webp'
extractExtension('/vol/images/photo.svg');   // '.jpg' (svg not in default allowed list)
extractExtension('image.svg', ['.jpg', '.png', '.svg']);    // '.svg'
```