why are objects wrapped in parenthesis in JS?

Question

Given the following example:

var foo = {
    root:
        ({
            key1: "Value1",
            key2: "Value2",
            key3: "Value3"
        })
    };

What is the difference compared to the following:

var foo = {
    root:
        {
            key1: "Value1",
            key2: "Value2",
            key3: "Value3"
        }
    };

In the first example there is an additional parens wrapping the object. What purpose does this serve? Does it have anything to do with scoping? Does it influence the execution in any way? Thank you!

There's no difference. In both cases `typeof(foo.root)` return `object` but I've never seen the first syntax — Fabrizio Calderan, Sep 20 '12 at 09:02
Interesting, didn't know you could do that, i don't think there is a difference. Wonder what other have to say about this. — Shikyo, Sep 20 '12 at 09:04
I stared at both of the examples for half a minute and then had to read the text to actually see the difference.. Good question! — Eric Lennartsson, Sep 20 '12 at 09:11
Does this answer your question? [Parentheses in an object literal](https://stackoverflow.com/questions/42870398/parentheses-in-an-object-literal) — Lucas Pottersky, Jul 28 '20 at 12:51

score 7 · Accepted Answer · edited May 23 '17 at 12:15

7

There is absolutely no difference here.

AFAIK the one place where it does make a difference is when you evaluate an object literal on the console.

edited May 23 '17 at 12:15

Community

1
1

answered Sep 20 '12 at 09:03

Jon

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score 2 · Answer 2 · answered Sep 20 '12 at 09:03

2

They do nothing :) They're there for readability, although it's questionable if they achieve that aim.

answered Sep 20 '12 at 09:03

Nick

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score 2 · Answer 3 · answered Sep 20 '12 at 09:34

As per me, we should use square brackets to collect the objects. because, JavaScript will understand that it is an array.

Round brackets(used in example 1) are just validated by the javasript parser. When you try to access it, java script returns Only last object in the round brackets(like top object in the stack).

Try below script

var foo = {
    root1:
        {
            key1: "Value1",
            key2: "Value2",
            key3: "Value3"
        },
    root2:({
            key4: "Value4",
            key5: "Value5"
          },{
            key6: "Value6",
            key7: "Value7"
        }),
    root3:[
         {
            key8: "Value8",
            key9: "Value9"
          },{
            key10: "Value10",
            key11: "Value11"
          }
    ]
    };
    console.log(foo['root1']);  // returns object { key1, key2, key3}
    console.log(foo['root2']);  // returns only { key6,key7}
    console.log(foo['root3']);  //returns [ {key8,key9},{key10,key11}]

why are objects wrapped in parenthesis in JS?

3 Answers3

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