In my node app i have to construct an object array from another object array.

Consider my object array as..

[ { id_0: 356, id_1: 33, name_1: 'aaaa' },
  { id_0: 756, id_1: 89, name_1: 'bbbbb' },
  { id_0: 456, id_1: 89, name_1: 'ccccc' },
  { id_0: 356, id_1: 27, name_1: 'dddd' } ]

I have to construct an object array as like below:

[{
"356":["33":"aaaa","27":"ddddd"],------------->Changes made
"456":[{"89":"cccc"}],
"756":[{"89":"bbbbbbbb"}]
}]

I tried using async.map.But i cant get the right way to do it.Please help me to solve this.Thanks in advance...

In my node app i have to construct an object array from another object array.

Consider my object array as..

[ { id_0: 356, id_1: 33, name_1: 'aaaa' },
  { id_0: 756, id_1: 89, name_1: 'bbbbb' },
  { id_0: 456, id_1: 89, name_1: 'ccccc' },
  { id_0: 356, id_1: 27, name_1: 'dddd' } ]

I have to construct an object array as like below:

[{
"356":["33":"aaaa","27":"ddddd"],------------->Changes made
"456":[{"89":"cccc"}],
"756":[{"89":"bbbbbbbb"}]
}]

I tried using async.map.But i cant get the right way to do it.Please help me to solve this.Thanks in advance...

• javascript
• node.js

Share Follow edited Apr 9, 2014 at 7:23 thefourtheye 240k5353 gold badges466466 silver badges501501 bronze badges asked Apr 9, 2014 at 6:28 SubburajSubburaj 5,2021111 gold badges4747 silver badges9595 bronze badges 2

• What's the point of using async here? – Leonid Beschastny Commented Apr 9, 2014 at 6:34
• It is Array.map() not async.map() and you don't usually call it that way, but as a method on an instance of an array. – Paul Commented Apr 9, 2014 at 6:35

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1 Answer 1

Sorted by: Reset to default 5

You can use Array.prototype.reduce function, like this

console.log(data.reduce(function(result, current) {
    var obj = {};
    result[current.id_0] = result[current.id_0] || [];
    obj[current.id_1] = current.name_1;
    result[current.id_0].push(obj);
    return result
}, {}));

Output

{ '356': [ { '33': 'aaaa' }, { '27': 'dddd' } ],
  '456': [ { '89': 'ccccc' } ],
  '756': [ { '89': 'bbbbb' } ] }

If you want to convert this to an array of object, just wrap the result of data.reduce with [] like this

console.log([data.reduce(function(result, current) {
    ...
    ...
}, {})]);

Edit:

result[current.id_0] = result[current.id_0] || [];

this line makes sure that result[current.id_0] is an array. If the value of result[current.id_0] is truthy, then that value is rturned but if it is not, then [] will be returned. So, a new array will be created and assigned to result[current.id_0]. It is actually a shorthand for

if (result.hasOwnProperty(current.id_0) === false) {
    result[current.id_0] = [];
}

Edit 2: If you like to keep the grouped elements as an object, you could do like this

console.log(data.reduce(function(result, current) {
    result[current.id_0] = result[current.id_0] || {};
    result[current.id_0][current.id_1] = current.name_1;
    return result
}, {}));

Output

{ '356': { '27': 'dddd', '33': 'aaaa' },
  '456': { '89': 'ccccc' },
  '756': { '89': 'bbbbb' } }