Skip to main content

index-by

$index-by​

Groups an array of objects by a unique key, returning an object whose value is the single array element value that has that key. If the keys are not unique, throws an error.

  • {'$index-by': 'key'} — indexes by the named property on each element
  • {'$index-by': processor} — indexes by the result of executing the processor against each element

Elements where the extracted key is undefined are omitted from the result.

Parameters​

  • key (string): Property name to group by, or a processor that extracts the grouping key from each element. If you use a bare argument or a single element array, it is assumed to be the key.
  • processor: Must be passed via object parameter. Must be a processor that will parse the provided element and return the index key. The outer collection is passed to the processor as options.input.

Example​

// TODO