Why doesn't JSON.stringify include array in output JSON object?

Question

If I open this in a browser:

<!DOCTYPE html>
<html>
    <head>
        <title>Testing stringify</title>
    </head>
    <body>
        <script>
            var obj = {};
            var arr = [];
            arr.push(1,2);
            alert(arr); // 1,2
            Object.defineProperty(obj, "name", {
                value:arr
            });
            alert(obj.name); // 1,2
            alert(JSON.stringify(obj)); // {}
        </script>
    </body>
</html>

it will output what I've written in the comments. I don't understand why arr isn't included in the output JSON-string. Do I need to define some other properties on the descriptor object in defineProperty()? What am I doing wrong?

score 3 · Accepted Answer · 2017-11-21 14:38:16Z

3

The property you made is non enumerable. Set enumerable: true in the descriptor and it'll work.

var obj = {};
var arr = [];
arr.push(1, 2);
console.log(arr); // 1,2
Object.defineProperty(obj, "name", {
  value: arr,
  enumerable: true,
});
console.log(obj.name); // 1,2
console.log(JSON.stringify(obj)); // {}

edited Nov 21, 2017 at 14:38

answered Nov 21, 2017 at 14:36

user8897421

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2 Comments

Sahand Over a year ago

Thanks. Why does the property need to be enumerable?

user8897421 Over a year ago

@Sandi: Basically because the stringify method needs to enumerate the properties in order to find them and add them to the JSON result. I imagine they must have made this design decision in order to be able to easily exclude properties.

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