Should I use a JSON Array or an Object?

Question

I have the following code :

$.each( orderedqty, function( priority, quantity ) {

    // for each priority

    if ( $(".switch[data-priorityid=" + priority + "]").attr("data-state") == "on" ) {

        // this priority is checked

        orderedqtyArray[ priority ] = 15;

    } else {

        orderedqtyArray[ priority ] = 10;

    }

});

console.info( orderedqtyArray );
console.info( JSON.stringify( orderedqtyArray ) );

The problem is this code returns :

[77: 15, 78: 15]
[null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,15,15]

[78: 15]
[null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,15]

Instead of a beautiful json :(

So you're creating a sparce array and when you convert it to JSON you get … a sparce array. What's the problem? — Quentin
– Quentin, Commented Oct 8, 2014 at 9:46
If you're referring to the fact that the stringify output lacks the keys "77: " & "78: " this will be due to the fact that they're integers and will be taken as array indices. — Chris Peacock
– Chris Peacock, Commented Oct 8, 2014 at 9:51
You can replace null with an empty string if you aren't expecting null in the string result. JSON.stringify(orderedqtyArray).replace(/null/g, "") — Mihir
– Mihir, Commented Oct 8, 2014 at 9:56

Tim Jansen · Accepted Answer · 2014-10-08 11:32:40Z

6

The browser's console.log output is optimized to remove the nulls, but it's the same array. JSON can't do this, it always includes all the nulls in the array.

If you want the stringified output to look more like console.log's, then you need to define it as an object and not as an array.

var a = [], b = {};
a[5] = 1;
b[5] = 1;
console.log(JSON.stringify(a));
console.log(JSON.stringify(b));

The output will be

[null, null, null, null, null, 1]
{"5": 1}

edited Oct 8, 2014 at 11:32

answered Oct 8, 2014 at 9:52

Tim Jansen

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Comments

Artemis · Accepted Answer · 2014-10-08 09:51:08Z

3

Something strange. But you should be aware of interesting behaviour of arrays in Js.

If you define something like this:

var array = [];
//defining item at arbitrary position
array[5] = 5;


// output from array will look something like this
 [undefined, undefined, undefined, undefined, 5]

So perhaps your orderedqtyArray[ priority ] sets value at some random index and it leads to the problem. Because if you would have normal array it would definitely stringify into valid json.

answered Oct 8, 2014 at 9:51

Artemis

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2 Comments

Chris Peacock Over a year ago

+1, please see my comment above also - you're using integers as your keys in orderedqtyArray, therefore making JavaScript think that you want an array (or maybe you do).

Artemis Over a year ago

sure it might be an Object for sure.

xShirase · Accepted Answer · 2014-10-08 09:50:19Z

2

If you just want to remove the null values, you can do :

JSON.stringify( orderedqtyArray.filter(function(e){return e}));

answered Oct 8, 2014 at 9:50

xShirase

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1 Comment

Artemis Over a year ago

But it makes no sense, we should avoid getting of these null values.

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