How can I add structure to an object created as the result of a db query

Question

I have a bit of code that draws from a Taffy db, to create an object that I then iterate through. In previous versions, the order of the elements in the object were consistent in their order (although I realize this is not guaranteed in js), so I was accessing them through this[0], this[1], etc. In the new version (apparently due to a Taffy bug, https://github.com/typicaljoe/taffydb/issues/109), this behaviour is not reliable, so I would like to know if there is a more robust way to structure the information and retrieve it. A minimal example:

var stuffWeCite = TAFFY([{
 "first": 1,
 "second": 2,
 "third": 3,
 "fourth": 4
 }]);

var filterVar = {"first":1};
var someVar = stuffWeCite()
.filter(filterVar)
.select("first", "second", "third", "fourth");

console.log('someVar: ' + someVar);

Previously, the result would appear 1, 2, 3, 4, but the behaviour has changed.

If I were entering the elements of the query into an object one-by-one, I would assign them properties ("first", "second", etc.) and then call those later, but the way they are selected seems to preclude this. Is there a way I can assign properties to the values when creating the object from a db query?

Ahmet Cetin · Accepted Answer · 2016-01-08T19:30:42.697

I don't know taffy, but for such kind of problem, i use an array helper, as you mentioned the order of the object keys are not reliable in javascript. You can declare an array which keeps the keys of the object in the order that you would like to use, then iterate it to get the values in the order from the object:

var stuffWeCite = TAFFY([{
    "second": 2,
    "first": 1,
    "fourth": 4
    "third": 3,
}]);

var array = ['first', 'second', 'third', 'fourth'];

array.forEach(function(item) {
    console.log(stuffWeCite[item]);
});

or with for loop:

var stuffWeCite = TAFFY([{
    "second": 2,
    "first": 1,
    "fourth": 4
    "third": 3,
}]);

var array = ['first', 'second', 'third', 'fourth'];

for (var i = 0, l = array.length; i<l; i++) {
    console.log(stuffWeCite[array[i]]);
}

For iterating through set of objects received from db, considering no. of fields you want to use small, so not necessary to iterate array:

var friendsInSeattle = friends({city:"Seattle, WA"});
var fieldsInOrder = ['id', 'gender', 'first', 'last'];

friendsInSeattle.forEach(function(friend) {
    console.log({
        fieldsInOrder[0]: friend(fieldsInOrder[0]),
        fieldsInOrder[1]: friend(fieldsInOrder[1]),
        fieldsInOrder[2]: friend(fieldsInOrder[2]),
        fieldsInOrder[3]: friend(fieldsInOrder[3])
    });
});

Of course you can construct the object while you iterate the fields array, if you have more fields, or fields may change in the future. Hope this helps.

I am running a very small db (a few hundred entries), but doesn't this approach vastly increase the computing overhead, by requiring multiple calls on the database for every element of output? For context, I was previously calling the db once, then iterating through the resulting object and using `this` to print the values. Doing it this way, it seems like I would need to call the db up to 160 times per query--is this a significant slowdown? — larkvi, Jan 08 '16 at 19:16
Not really, as i understand taffydb is memory-based db, so all operation db requests, etc, happening in memory, therefore there shouldn't be much trouble for speed, as there won't be waiting time over a cable or harddisk access. But anyway, you can still query db once, get the recordset, and iterate through both recordset and the fields array. I just added small example above. Of course there is a overhead adding another iteration for the fields, but I would consider it negligible to get the result you want, and it's sure thing, and won't rely on the order in object keys. — Ahmet Cetin, Jan 08 '16 at 19:33
I highly suggest not to rely on order in js object keys. it might surprise you a lot, using different browsers, libraries, etc., and they regularly update, and as key order in object is not enforced in standard, it's highly unreliable, they can break it in next version without breaking the ecma standard. — Ahmet Cetin, Jan 08 '16 at 19:37

How can I add structure to an object created as the result of a db query

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