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