Unique sub-Json of a Json - json

Question

let me start from a JSon object like
[
{
"id": 32837732,
"composer": {
"id": 536,
"name": "Francis Poulenc"
},
"title": "Of Thee I Sing: Overture (radio version)"
},
{
"id": 32837735,
"composer": {
"id": 245,
"name": "George Gershwin"
},
"title": "Concerto in F : I. Allegro"
},
{
"id": 32837739,
"composer": {
"id": 245,
"name": "George Gershwin"
},
"title": "Concerto in F : II. Adagio"
}
]
is it possible to get, in a clean, declarative way, a Json like
{
'composer': [
{
'id': '536',
'name': 'Francis Poulenc'
},
{
'id': '245',
'name': 'George Gershwin'
},
]
}
That is the unique sub-values for each composer (id and name)?

Answer 1

var arr= [
{
"id": 32837732,
"composer": {
"id": 536,
"name": "Francis Poulenc"
},
"title": "Of Thee I Sing: Overture (radio version)"
},
{
"id": 32837735,
"composer": {
"id": 245,
"name": "George Gershwin"
},
"title": "Concerto in F : I. Allegro"
},
{
"id": 32837739,
"composer": {
"id": 245,
"name": "George Gershwin"
},
"title": "Concerto in F : II. Adagio"
}
];
var composers=[];
arr.forEach(function(arrElem){
if(arrElem.composer && !composers.some(function(comp) { return comp.id === arrElem.composer.id && comp.name === arrElem.composer.name }))
composers.push(arrElem.composer);
});
alert( JSON.stringify( composers ));