Merge array of javascript objects by property key

Question

First of all: I already found this thread, which basically is exactly what I want, but I tried my best to apply it to my needs - I couldn\'t.

So, I have the followin

Answer 1

Try this:

function joinObjects( array ) {

    // Start with empty array
    var ret = new Array();

    // Iterate array
    for ( var i = 0; i < array.length; i++ ) {

        // Search by fieldname
        var match = false;
        var j;
        for ( j = 0; j < ret.length; j++ ) {
            if ( array[i].Fieldname == ret[j].Fieldname ) { match = true; break; }
        }

        // If not exists
        if ( !match ) {

            // Intert object
            ret.push({
                Fieldname: array[i].Fieldname,
                Value: new Array()
            });

        }

        // Insert value
        ret[j].Value.push( array[i].Value );

    }

    // Return new array
    return ret;

}

http://jsfiddle.net/6entfv4x/

Answer 2

What you'd want to do first is build a hash with Fieldname as key, and an array as value. Then you'd want to use reduce to add the values into the hash and array. Then you can transform it into an array using Object.keys and map.

var input = [
  {Name: 'M100', ObjectID: 1, ObjectType: 'TEC_MapLocation'},
  {Name: 'M200', ObjectID: 2, ObjectType: 'TEC_MapLocation'},
  {Name: 'FL456', ObjectID: 4, ObjectType: 'TEC_FunctionalLocation'},
  {Name: 'E0192', ObjectID: 5, ObjectType: 'TEC_Equipment'}
];

var hash = input.reduce(function(carry, item){
  
  // Create the name
  var name = 'Übergeordnete ' + item.ObjectType;

  // If array with name doesn't exist, create it
  if(!carry[name]) carry[name] = [];

  // If item isn't in the array, add it.
  if(!~carry[name].indexOf(item.Name)) carry[name].push(item.Name);

  return carry;
}, {});

// Convert the hash into an array
var output = Object.keys(hash).map(function(key, index, array){
  return { Fieldname: key, Value: hash[key] }
});

document.write(JSON.stringify(output));