External module "utils/object-inverse-by/docs/types/index.d"

Export assignment invertBy

• invertBy(obj: any, transform: Transform): any
• invertBy(obj: any, options: Options, transform: Transform): any

• Inverts an object, such that keys become values and values become keys, according to a transform function.

  Notes

  • The transform function is provided three arguments:

    • key: object key
    • value: object value corresponding to key
    • obj: the input object

  • The value returned by a transform function should be a value which can be serialized as an object key. Hence, beware when providing objects having values which are themselves objects. The function relies on native object serialization (#toString) when converting transform function return values to keys.

  • Insertion order is not guaranteed, as object key enumeration is not specified according to the ECMAScript specification. In practice, however, most engines use insertion order to sort an object's keys, thus allowing for deterministic inversion.

  Parameters

  • obj: any

    input object

  • transform: Transform

    transform function

  Returns any

  inverted object

  Example

  function transform( key, value ) {
      return key + value;
  }
  var obj = {
      'a': 'beep',
      'b': 'boop'
  };
  var out = invertBy( obj, transform );
  // returns { 'abeep': 'a', 'bboop': 'b' }

  Example

  function transform( key, value ) {
      return value;
  }
  var obj = {
      'a': 'beep',
      'b': 'beep'
  };
  var out = invertBy( obj, transform );
  // returns { 'beep': [ 'a', 'b' ] }

• Inverts an object, such that keys become values and values become keys, according to a transform function.

  Notes

  • The transform function is provided three arguments:

    • key: object key
    • value: object value corresponding to key
    • obj: the input object

  • The value returned by a transform function should be a value which can be serialized as an object key. Hence, beware when providing objects having values which are themselves objects. The function relies on native object serialization (#toString) when converting transform function return values to keys.

  • Insertion order is not guaranteed, as object key enumeration is not specified according to the ECMAScript specification. In practice, however, most engines use insertion order to sort an object's keys, thus allowing for deterministic inversion.

  Parameters

  • obj: any

    input object

  • options: Options

  • transform: Transform

    transform function

  Returns any

  inverted object

  Example

  function transform( key, value ) {
      return value;
  }
  
  var obj = {};
  obj.a = 'beep';
  obj.b = 'boop';
  obj.c = 'beep'; // inserted after `a`
  
  var opts = {
      'duplicates': false
  };
  var out = invertBy( obj, opts, transform );
  // returns { 'beep': 'c', 'boop': 'b' }