Javascript object that maps keys to value & allows iteration over keys

Question

I need to create object in javascript that allows to fetch values using keys & also iterate over keys. The primary requirement is fetching value by key but iteration is required to maintain sort order of entries by values(integer).

How do I go about creating such an object ?

check this post here http://stackoverflow.com/questions/1078118/how-to-iterate-over-a-json-structure — ManMohan Vyas, Sep 24 '12 at 05:32
@ManMohan Vyas: just iteration is ok, but how to retrieve value by key ? — Rajat Gupta, Sep 24 '12 at 05:36
@user01: Retrieve value by key is easy: the most general way is obj['keyname'], a less general way is obj.keyname — nhahtdh, Sep 24 '12 at 05:37
@nhahtdh: Thanks. Please also suggest a way to append entries to `sampleJson={ "1":"john", "2":"johny" }` to add `"3":"johnyoo"` — Rajat Gupta, Sep 24 '12 at 05:53
@user01: You should get a good book on JS before even start coding. As for that sampleJson['3'] = "johnyoo". But the problem is, normal JS Object won't fulfill your second condition of "maintain sort order of entries by values(integer)" while allow fetching by key. — nhahtdh, Sep 24 '12 at 05:56
@user01 http://stackoverflow.com/questions/6503193/nested-json-how-to-add-push-new-items-to-an-object check that — ManMohan Vyas, Sep 24 '12 at 05:56

score 1 · Answer 1 · answered Sep 24 '12 at 05:29

1

All objects in JavaScript are JSONeable! (is that really a word).
All objects in JavaScript are a collection of key value mappings.
A for in loop iterates over the keys of an object.

answered Sep 24 '12 at 05:29

ColinE

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1

Your answer does not answer the question: "maintain sort order of entries by values(integer)." – nhahtdh Sep 24 '12 at 05:31

score 1 · Accepted Answer · answered Sep 24 '12 at 05:33

1

sampleJson={
"1":"john",
"2":"johny"
}

You can iterate using for in loop

for(key in sampleJson){
//ur code
}

answered Sep 24 '12 at 05:33

Apurv

309
2
10

how to retrieve value by key ? for eg, when querying with "1" as key it should give "john" – Rajat Gupta Sep 24 '12 at 05:34
Do you read the question carefully? There is also the part: "maintain sort order of entries by values(integer)." – nhahtdh Sep 24 '12 at 05:35
for(key in sampleJson){alert(sampleJson[key])} – Apurv Sep 24 '12 at 05:37

score 0 · Answer 3 · answered Sep 24 '12 at 06:44

Native objects don't support exactly what you're looking for, but it's fairly straightforward to create a wrapper around native objects that provides extra functionality.

A possible approach:

function KeySortArr(obj) {
    this.obj = obj || {};
}

KeySortArr.prototype = {
    get: function(key) {
        return this.obj[key];
    },

    set: function(key, value) {
        this.obj[key] = value;
    },

    keys: function() {
        var keys = [];
        for(var i in this.obj) {
            if (this.obj.hasOwnProperty(i))
                keys.push(i);
        }
        return keys;
    },

    getKeysSortedByValue: function() {
        var obj = this.obj;
        return this.keys().sort(function(a, b) {
            return obj[a] > obj[b];
        });
    }
};

Usage:

var arr = new KeySortArr();
arr.set("test", 4);
arr.set("another", 2);
arr.set("ok", 60);
arr.set("last", 14);

The following then:

arr.getKeysSortedByValue();

Returns:

["another, "test", "last", "ok"]

In other words, the keys are sorted by their associated value. This might not be exactly what you were looking for, but it should be close.

Javascript object that maps keys to value & allows iteration over keys

3 Answers3