what is the purpose of using square brackets in json?

Question

I am new to json. Some json examples i have seen have data within the curly braces and some json examples have subdata within square brackets.

{
"glossary": {
    "title": "example glossary",
    "GlossDiv": {
        "title": "S",
        "GlossList": {
            "GlossEntry": {
                "ID": "SGML",
                "SortAs": "SGML",
                "GlossTerm": "Standard Generalized Markup Language",
                "Acronym": "SGML",
                "Abbrev": "ISO 8879:1986",
                "GlossDef": {
                    "para": "A meta-markup language, used to create markup languages such as DocBook.",
                    "GlossSeeAlso": ["GML", "XML"]
                },
                "GlossSee": "markup"
            }
        }
    }
}
}

From http://json.org/example.html

What is the need/purpose of having data within the square brackets?

regards

@Quentin my question differed from the question suggested as duplicate. — Uswer721, Apr 18 '16 at 08:31
No, it doesn't. You are asking what the difference between `[]` and `{}` is, that question is asking what the difference between `[]`, `{}` and `new Array()` is. That's as close to identical as makes no practical difference. — Quentin, Apr 18 '16 at 08:37
@Quentin Maybe. I thought [ ] **within** { } had a different significance. No problemo, i got it now. — Uswer721, Apr 18 '16 at 08:56
The distinction of using a JSON example was important to me. I suppose it's ok to be marked a dupe as long as the question remains available. — MrBoJangles, Jan 22 '18 at 20:29
What a weak reason for something to be a duplicate... I see where that's coming from, but that assumes you know that javascript and json are practically the same thing, otherwise it will seem odd. — Broots Waymb, Feb 09 '18 at 20:38
This explains things in great detail and thoroughly answers the question: https://stackoverflow.com/a/5034547/1854328 — Robert Mauro, Feb 01 '19 at 15:38

score 84 · Accepted Answer · edited Oct 04 '19 at 14:07

84

The square brackets produce a list/array.

The curly brackets produce an object with key/value pairs.

The list can then be a value of a key/value pair.

edited Oct 04 '19 at 14:07

jvyden

89
1
7

answered Apr 18 '16 at 08:01

Boy

7,010
4
54
68

doesn't the "product" depends on the implementation of deserializing function in each language ? Isn't json just a few rules for plain text ? I thought only programming languages can have rules for "producing datatypes or objects" – illevens Oct 11 '21 at 15:05

score 64 · Answer 2 · edited Sep 17 '17 at 05:18

64

[] means an array of object (a list) and {} means it will be an object.

Example:

{
    "ID":"test",
    "sports": [
        "volley-ball",
        "badminton"
    ]
}

To get the ID, you can do: myjsonobject.ID (here you will get "test")

And for sports: myjsonobject.sports[0] (here you will get "volley-ball")

edited Sep 17 '17 at 05:18

Community

1
1

answered Apr 18 '16 at 08:04

Samuel LEMAITRE

1,041
7
8

6

The example makes the concept of { } and [ ] clear. Thanks! – Uswer721 Apr 18 '16 at 08:49
1

In other words, [ ] is an array, and { } is a hashtable. For the PowerShell guys, [ ] equals @( ), while { } equals @{ }. – bviktor Mar 10 '18 at 18:58

what is the purpose of using square brackets in json?

2 Answers2

Linked