CODEWITHSUNDEEP
javascriptjson
Xuhang
Xuhang

Reputation: 495

JSON stringify array of objects with property

I was trying to stringify a array of objects with extra properties.

var data = [{foo: "1", bar: "2"}, {foo: "2", bar:"3"}];
data.extra = ["a", "b"];

console.log(data)
// [{foo: "1", bar: "2"}, {foo: "2", bar:"3"}, extra: ["a", "b"]]

console.log(JSON.stringify(data));
//[{foo: "1", bar: "2"}, {foo: "2", bar:"3"}]

Q: Why is the "extra" property not stringified? How can I preserve the missing property in JSON.stringify()?

Upvotes: 1

Views: 4991

Answers (4)

raina77ow
raina77ow

Reputation: 106365

Because data is not just an Object - it's an Array. And when Arrays are json-stringified, all the non-numeric properties are discarded from result (as there's no way to represent them in [...] notation anyway).

If you still want to see that property in JSON, you have to use plain Objects. You can bite the bullet and just "plain-objectify" the original array with { ... } sugar:

const data = [{foo: "1", bar: "2"}, {foo: "2", bar:"3"}];
data.extra = ["a", "b"];
JSON.stringify( {...data} );
// "{"0":{"foo":"1","bar":"2"},"1":{"foo":"2","bar":"3"},"extra":["a","b"]}"

... but beware, all those "0", "1" props will be seen inside your JSON as is, and that's not the best of views. It's usually cleaner just to use additional property:

const data = [{foo: "1", bar: "2"}, {foo: "2", bar:"3"}];
const extra = ["a", "b"];
const output = {
  data,
  extra
};
JSON.stringify(output);
// "{"data":[{"foo":"1","bar":"2"},{"foo":"2","bar":"3"}],"extra":["a","b"]}"

Upvotes: 3

Matteo Dal Grande
Matteo Dal Grande

Reputation: 120

{...} is used to define a single object, while the other [...] is array and is used to define a sequence of either objects, values or lists ...

objects are defined as such {key:object or list or value , ...} list ares nothing more than a sequence of either objects or lists or values, [objects or list or values, ... ]...

try to use single object and not array.

Upvotes: 0

hossein sedighian
hossein sedighian

Reputation: 2035

your json is Array but you put one key to them

if you want to use it with keyword you should use :

var data = [{foo: "1", bar: "2"}, {foo: "2", bar:"3"}];
data.push(["a", "b"]) ;

console.log(data)
// [{foo: "1", bar: "2"}, {foo: "2", bar:"3"}, extra: ["a", "b"]]

console.log(JSON.stringify(data));
//[{foo: "1", bar: "2"}, {foo: "2", bar:"3"}]

Upvotes: 0

Tomer Levitski
Tomer Levitski

Reputation: 111

You can put the extra:[ ... ] inside { } wgich will make at in object. Then you can stringify it.

Upvotes: 0

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