How to correctly populate an associative array dynamically in Javascript

Question

I am trying to build arrays within an array and I would like to be able to access the stored data through array[x][y]. I have a sample code below that I can't get to work the way I want and I wonder if anyone can spot the problem.

$.getJSON("/data/", function(data){

    var test = {};
    var levels = [1,2,3];

    $.each(data, function(key, value){

        var cat = data[key];

        $.each(levels, function(li,l){

            var base = cat[2];
            var keys = Object.keys(base);

            if (l == 1) {

                test[l] = {};

                $.each(keys, function(ki,k){
                    test[l][k] = base[k][0];
                });
            }

        });

    });

    alert(Object.keys(test[1]));

});

The structure of the fetched JSON data is as shown here:

{
    "1": ["Distribution", 0,
    {
        "9": ["Salmonella", 0,
        {}],
        "6": ["E. coli", 0,
        {
            "8": ["from pigs", 0,
            {}],
            "7": ["from humans", 0,
            {}]}]}],
    "2": ["Adhesin", 0,
    {
        "1": ["PapG", 1,
        {
            "2": ["has three subtypes:", 0,
            {
                "3": ["PapG-I", 0,
                {}],
                "4": ["PapG-II", 0,
                {}],
                "5": ["PapG-III", 0,
                {}]}]}]}],
    "3": ["Receptors", 0,
    {}],
    "4": ["Disease associations", 0,
    {}],
    "5": ["Regulation", 0,
    {}]
}

The code above doesn't seem to store values to the array within the test array as alert(Object.keys(test[1])) doesn't give anything (i.e. just blank alert).

Edit: after the mistakes spotted by Oleg V. Volkov (below):

$.getJSON("/data/", function(data){

        var test = {};
        var levels = [1,2,3];

        $.each(data, function(key, value){

               // var cat = data[key];

               $.each(levels, function(li,l){

                     var base = value[2];
                     var keys = Object.keys(base);

                     if (l == 1) {

                          if ($.inArray(l,test) == -1){ 
                              test[l] = {};
                          }

                          $.each(keys, function(ki,k){
                             test[l][k] = base[k][0];
                          });
                      }

               });

        });

        alert(Object.keys(test[1]));

});

Still not working.

@VisionN - Right. I corrected it now to show the JSON format. — joemar.ct
– joemar.ct, Commented May 12, 2012 at 9:59
I recommend to set breakpoints in your code, go through it step by step and inspect the variables. — Felix Kling
– Felix Kling, Commented May 12, 2012 at 10:15
@FelixKling - I have been doing it. So far, I can't pin down where it's going wrong. A few more tries needed. — joemar.ct
– joemar.ct, Commented May 12, 2012 at 10:36

Oleg V. Volkov · Accepted Answer · 2012-05-12 12:57:58Z

1

var cat = data[key];

You don't need this line. Your data is already in value.

You're overwriting same test[l] values on each iteration, so in the end you will only have result of the last outermost iteration in it - in many browsers that will be one that goes over "5": ["Regulation", 0, {}] key/value pair. Quick look over you code suggest cat[2] will be {} for it and that so last iteration will overwrite anything in test[] with empty objects. So your keys correctly returns empty list, but you have an error in your logic.

Regarding your updated example: You're still overwriting test entries with {} because you use .inArray to check it and it will always succeed in not finding any number value in array. .inArray looks for a specific value, not keys/indexes. You should check if specific index is empty instead with if(!test[l])

edited May 12, 2012 at 12:57

answered May 12, 2012 at 11:11

Oleg V. Volkov

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3 Comments

joemar.ct Over a year ago

I edited the code (shown above) taking into account the mistakes you have observed. Still not working.

Oleg V. Volkov Over a year ago

What exactly do you want to do with your data? Intent of your code is not exactly clear to me.

joemar.ct Over a year ago

The data is hierarchical with tree-like structure. In every level in the hierarchy, I want to store a chunk of info about each member into a single associative array. Each member has a unique id. In the end, I want to be able to access each chunk through array[level][member_id]. The code above does not exactly do what I want to do. It is just oversimplified to replicate the issues I'm experiencing.

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