Function storage_key

storage_key(params: { index: number; type?: string }): Promise<string | null>
Retrieves the key at the specified index.
Parameters
- params: { index: number; type?: string }
  The named parameters
  - index: number
    
    The key entry to look up.
  - Optionaltype?: string
    
    The storage to act upon.
Returns Promise<string | null>
The key at the specified index or null if beyond the storage capacity. A rejected promise represents an API violation.
Example
```
// Make sure it is available to the runtime.
if (runtime_available({request: AVAILABILITY_REQUEST.Local})) {
  // To get a key at an index. Either string or null if not found
  // Defaults to STORAGE_TYPE.Local
  let key = await storage_key({index: 0});
  // To specify type
  let key = await storage_key({type: STORAGE_TYPE.Session, index: 0});
}
```