JSON.stringify returns [] when converting object to json

Question

I am struggling to create a JSON object to send over the wire. The Array in question looks like this in the Chrome debugger.

event: Array[0]
        $$hashKey: "02Q"
        bolFromDB: 1
        bolIndoor: null
        classId: 41
        curValue: "7.1000"
        curWeightHeight: ""
        datDate: "2013-01-13T01:00:00.000Z"
        exists: true
        id: "10"
        idClass: "W"
        idEvent: "60M"
        length: 0
        ownEvents: true
        ownSex: true
        pbs: undefined
        selected: true
        strAdditional: ""
        strName: "60m"
        strTown: "Stadtallendorf"
__proto__: Array[0]

This is a small part of a much bigger object array, but in trying to break the problem down to it's smallest part, this appears to be the end of the line.

When calling JSON.stringify(event), the value returned is [].

I expected {$$hashKey: "02Q",bolFromDB: 1, bolIndoor: null, ... etc }

It would help if you could show us how event is created

Explosion Pills
– Explosion Pills

2013-12-23 17:10:19 +00:00
Commented Dec 23, 2013 at 17:10 — Explosion Pills
– Explosion Pills, Commented Dec 23, 2013 at 17:10

Community · Accepted Answer · 2017-05-23 12:03:44Z

5

It looks like your event object was initialised as an Array and was then assigned alphanumeric keyed properties. JavaScript Arrays will accept non-numeric keys, but the JSON parser will ignore these, because JSON has to use square bracket notation for Arrays and as such the numeric keys are implicit — it's impossible to express named properties using square brackets notation.

Zach L wrote a couple of tests to validate this assertion:

var test = [];
test.prop = 'foo';
console.log(test);   // [prop: "foo"] 
test                 // []
JSON.stringify(test) // "[]"

That's JSON showing an empty Array. However, when we start with an object:

var test = {};
test.prop = 'foo';
console.log(test);   // Object {prop: "foo"}
test                 // Object {prop: "foo"}
JSON.stringify(test) // "{"prop":"foo"}"

From what you're saying, it looks like it was never intended for event to be an Array, so I'd suggest you make sure to instantiate as an object before all these properties are assigned to it:

var event = {};

edited May 23, 2017 at 12:03

CommunityBot

11 silver badge

answered Dec 23, 2013 at 17:11

Barney

16.5k5 gold badges66 silver badges80 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Zach Lysobey Over a year ago

feel free to grab my examples below and append to your own answer if you feel its relevant and adds to yours. That way all info can be in a single canonical answer, and I can remove mine.

Collectives™ on Stack Overflow

JSON.stringify returns [] when converting object to json

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related