Issue with JSON stringify?

Question

/* Helper function to clean up any current data we have stored */
function insertSerializedData(ids, type) {
    // Get anything in the current field
    current_data = $('#changes').val();
    if (!current_data) {
        var data = new Array();
        data[type] = ids;
        $('#changes').val(JSON.stringify(data));
    } else {
        var data = JSON.parse($('#changes').val());
        data[type] = ids;
        $('#changes').val(JSON.stringify(data));
    }
    console.log($('#changes').val());
}

I am using the following function to either add data to a current JSON object or create a new JSON object all together to be used in PHP later. Is the stringify() method only for FF? I am using google chrome and I am being given an empty object when using the conosole.log() function...

Also what happens if you try to store two values with the same key? I assume it will overwrite...so I should add a random math number at the end array in order to keep duplicates from showing up?

Thanks :)

JSON.stringify does exist in Chrome and IE 8 and later. Your error is somehwere else. Try to call console.log(data) before calling JSON.stringify — Ruan Mendes
– Ruan Mendes, Commented Jun 22, 2012 at 0:14
random numbers don't guarantee uniqueness, they just reduce the probability that it will happen. If it's important, you should track your indexes and increase them as you go, to guarantee unique field names. — Yevgeny Simkin
– Yevgeny Simkin, Commented Jun 22, 2012 at 0:14
Here's a useful compatibility table for JSON parsing support: caniuse.com/json — Cecchi
– Cecchi, Commented Jun 22, 2012 at 0:15
Your line that says var data = new Array() should be = new Object(), or even prettier = {}; An array is an ordered list, not a map, it's not PHP. — Ruan Mendes
– Ruan Mendes, Commented Jun 22, 2012 at 0:16
Also, don't ask two questions in one here at SO. You can easily verify that if you store two values with the same key, it will get overwritten. — Ruan Mendes
– Ruan Mendes, Commented Jun 22, 2012 at 0:18

raina77ow · Accepted Answer · 2012-06-22 00:23:39Z

2

These lines may cause problems:

var data = new Array();
data[type] = ids;

... because arrays in JavaScript are not quite like arrays in PHP. I suppose what you meant is better expressed by...

var data = {};
data[type] = ids;

Besides, current_data seems to be local to this function, therefore it also should be declared as local with var. Don't see any other problems... except that similar functionality is already implemented in jQuery .data() method.

UPDATE: here's jsFiddle to play with. ) From what I've tried looks like the array-object mismatch is what actually caused that Chrome behavior.

edited Jun 22, 2012 at 0:23

answered Jun 22, 2012 at 0:14

raina77ow

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1 Comment

Ruan Mendes Over a year ago

These are all valid comments, but none of them is an answer to the question.

Tim Christensen · Accepted Answer · 2012-06-22 00:26:18Z

0

I reformatted it a bit, but and this seems to work. It will set the "value" attribute of the #changes element to a JSON string. I assume that the type argument is supposed to be the index of the array which you're trying to assign?

function insertSerializedData(ids, type) {
  var changes = jQuery('#changes'), arr, val = changes.val();
  if (!val) {
    arr = [];
    arr[type] = ids;
    changes.val(JSON.stringify(arr));
  } else {
    arr = JSON.parse(val);
    arr[type] = ids;
    changes.val(JSON.stringify(arr));
  }
  console.log(changes);
}

answered Jun 22, 2012 at 0:26

Tim Christensen

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2 Comments

raina77ow Over a year ago

It would be a waste of memory using type as index, see. ) When var x = []; x[99] = 99; then x.length will be 100, even though the array is efficiently storing just a single element.

Tim Christensen Over a year ago

I feel that my solution functionally works, but I think you're right that it's sub-optimal. However, it's a drop in the bucket to have 100 items in an array.

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