How to convert from a JSON array to a JSON object

Question

I have this JSON that I'm getting back from a web service call:

{
    "name": "My Name",
    "path": "my path",
    "id": "44",
    "type": "my type",
    "classes": "my classes"
},
{
    "name": "his Name",
    "path": "his path",
    "id": "76",
    "type": "his type",
    "classes": "his classes"
}

I then need to convert it to this format

{
    "44" : { "name" : "My Name", "path" : "my path" },
    "76" : { "name" : "his Name", "path" : "his path" }
}

My initial naive attempt was this:

var myData = [];
for (var i = 0; i < rawData.length; i++) {
myData.push({
    rawData[i].id :
    {
        "path": rawData[i].path,
        "name": rawData[i].name
    }
});

which fails with syntax errors, so I eventually got to this:

var myData = [];
for (var i = 0; i < rawData.length; i++) {
myData.push(rawData[i].id,
{
    "path": rawData[i].path,
    "name": rawData[i].name
});

and it mostly works. My array is populated, but the problem is that my myData array doesn't have the "44", and "76" part of the object, just the { "name" : "", "path" : "" } part. I expect this is due to a lack of understanding on my part of how JSON and javscript objects work.

This has nothing to do with JSON. Those are arrays and objects, not text. — T.J. Crowder
– T.J. Crowder, Commented Apr 9, 2014 at 16:50

T.J. Crowder · Accepted Answer · 2014-04-09 16:51:18Z

1

Your desired output isn't an array, so that's your starting point. The output you've said you want is an object, not an array.

You build your result by creating a blank object and then adding the objects to it using id as the key:

var myData = {};
rawData.forEach(function(entry) {
    myData[entry.id] = {
        name: entry.name,
        path: entry.path
    };
});

Or if you don't want to use forEach (it's ES5, but can be shimmed for older browsers), the old-fashioned way:

var myData = {};
var index, entry;
for (index = 0; index < rawData.length; ++index) {
    entry = rawData[index];
    myData[entry.id] = {
        name: entry.name,
        path: entry.path
    };
}

answered Apr 9, 2014 at 16:51

T.J. Crowder

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1 Comment

Nate Over a year ago

Exactly what I was missing, after making the leap from array to object it makes perfect sense. Thanks.

MrCode · Accepted Answer · 2014-04-09 16:51:16Z

1

Don't use Array.prototype.push(), use the square bracket notation and define your output as an object not an array.

var myData = {};
for (var i = 0; i < rawData.length; i++) {
    myData[rawData[i].id] = {
        "path": rawData[i].path,    
        "name": rawData[i].name
    }
}

answered Apr 9, 2014 at 16:51

MrCode

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Comments

Kim T · Accepted Answer · 2014-04-09 16:51:09Z

0

You need to convert your id to a string?

var myData = {};
for (var i = 0; i < rawData.length; i++) {
    myData[String(rawData[i].id)] = {
        "path": rawData[i].path,
        "name": rawData[i].name
    };
}

answered Apr 9, 2014 at 16:51

Kim T

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1 Comment

T.J. Crowder Over a year ago

"You need to convert your id to a string?" No, it's already a string. And if it weren't, it would become one as soon as you used it as a property name ([...] notation).

Andy · Accepted Answer · 2014-04-09 16:52:17Z

0

A variation on what other posters have written:

// Create a new empty object.
var out = {};

// Loop over your array of objects
// Add the each object id as a key to the output object, and the object as the value.
for (var i = 0, l = arr.length; i <l; i++) {
  var obj = arr[i];
  out[obj.id] = obj;

  // Delete the properties from the newly added object you don't want.
  delete obj.id;
  delete obj.type;
  delete obj.classes;
}

answered Apr 9, 2014 at 16:52

Andy

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