async.map which works on objects

[tremby]

I had a use case just now for async.map which iterates on the values of an object, and whose callback has a new object with the original keys pointing to the translated values of the same keys.

async.map as it exists doesn't allow this, and I couldn't see another method which does the same (please let me know if I missed it).

I think it'd be useful feature.

In the mean time, I faked it with underscore by doing async.map(_.values(obj), ... and then in the callback using _.object(_.keys(obj), transformed).

[Volox]

+1

[glukki]

+1 For now I use this wrapper

function asyncObjectMap( obj, func, cb ) {
    var i, arr = [], keys = Object.keys( obj );
    for ( i = 0; i < keys.length; i += 1 ) {
        arr[i] = obj[keys[i]];
    }
    async.map( arr, func, function( err, data ) {
        if ( err ) { return cb( err ); }

        var res = {};
        for ( i = 0; i < data.length; i += 1 ) {
            res[keys[i]] = data[i];
        }

        return cb( err, res );
    } );
}

// test
asyncObjectMap(
    { a: 1, b: 2 },
    function( item, cb ) {
        console.log( item );
        cb( null, item );
    },
    console.log
);

[tremby]

It would be good to note the resolution of the ticket here -- reading through commit messages to find the answer is often not as easy as it sounds. Was this implemented or rejected?

[caolan]

@tremby closed in favour of #168 - which I know isn't a map but seems like the right approach rather than varying the number of arguments to iterators

[tremby]

Great -- thanks.

[JumpLink]

Another Version of @glukki 's Wrapper:

  async.objectMap = function ( obj, func, cb ) {
    var i, arr = [], keys = Object.keys( obj );
    for ( i = 0; i < keys.length; i += 1 ) {
      var wrapper = {};
      wrapper[keys[i]] = obj[keys[i]];
      arr[i] = wrapper;
    }
    this.map( arr, func, function( err, data ) {
      if ( err ) { return cb( err ); }
      var res = {};
      for ( i = 0; i < data.length; i += 1 ) {
          res[keys[i]] = data[i];
      }
      return cb( err, res );
    });
  }