How to merge these arrays/json objects?

Question

I am a bit confused at this point on what is an object, what is an array, and what is a JSON. Can someone explain the differences in syntax between the two? and how to add items to each, how to merge each type, and such? I am trying to get this function to take the new information from a JSON object (I think) and merge it with some new information. This information will then be passed to a PHP script to be processed.

Here is the console output:

{"public":{"0":["el29t7","3bmGDy"]}} 
{"public":"[object Object][object Object]"} 

Here is the JS I am using:

/* 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 = {};
        data[index++] = ids;
        var final_data = {};
        final_data[type] = data;
        $('#changes').val(JSON.stringify(final_data));
    } else {
        current_data = JSON.parse(current_data);
        var data = {};
        data[index++] = ids;
        // Does the index exist?
        if (type in current_data) {
            var temp_data = current_data[type];
            current_data[type] = temp_data + data;
        } else {
            current_data[type] = data;
        }
        //var extra_data = {};
        //extra_data[type] = data;
        //$.merge(current_data, extra_data);
        $('#changes').val(JSON.stringify(current_data));
    }
    console.log($('#changes').val());
}

The idea is if the key (public, or whatever other ones) doesn't exist yet, then to make it point to an array of arrays. If it does exist though, then that of array of arrays need to be merged with a new array. For instance:

If I have

{"public":{"0":["el29t7","3bmGDy"]}}  

and I want to merge it with

["aj19vA", "jO71Ba"] 

then final result would be:

{"public":{"0":["el29t7","3bmGDy"], "1":["aj19vA", "jO71Ba"]}} 

How can i go about doing this? Thanks

Answer 1

Excellent two-part question. Overall, the second question is non-trivial because of the complexity of the first.

Question 1:

what is an object, what is an array, and what is a JSON. Can someone explain the differences in syntax between the two?

Question 2:

and how to add items to each,

Question 3:

how to merge each type, and such?

Answer 1:

This is a common stumbling point because, JavaScript is more flexible than one might initially expect. Here is the curve.

In JavaScript everything is an object.

So here is the code for each:

//What is an object?
var obj = { };                

var obj2 = { member:"value", myFunction:function(){} }

Above is an empty object. Then another object with a variable and a function. They are called object-literals.

//What is an array 
var array1 = [ ] ;     

var array2 = [0,1,2,3,4];

Above is an empty array. Then another array with five Integers.

Here is the curve that causes confusion.

//Get elements from each of the prior examples.
var x = obj2["member"];
var y = array2[1];

What??? Both Object and Array are accessing values with a bracket? This is because both are objects. This turns out to be a nice flexibility for writing advanced code. Arrays are objects.

//What is JSON?

JSON stands for JavaScript Object Notiation. As you might have guessed. Everything is an object... It is also an { }; But it is different because - it is used to transfer data to - and - from JavaScript, not actually used (commonly) in JavaScript. It is a file transfer format.

var JSONObject = {"member":"value"};

The only difference to the prior example is quotes. Essentially we are wrapping the object literal as a string so that it can be transferred to a server, or back, and it can be reinterpreted, very easily. Better than XML - because it does not have to be custom-parsed. Just call, stringify() or ParseJSON(). Google it. The point is... JSON can be converted into an object-literal JS object, and JS object-literals can be converted into JSON, for transfer to a server or a CouchDB database, for example.

Sorry for the tangent.

Answer 2:

How to add an item to each? Here is where the curve stops being a nuisance, and starts being awesome! Because everything is an object, it is all just about the same.

//Add to an object
var obj {member1:"stringvalue"}
obj.member2 = "addme";    //That is it!

//Add to an array
var array1 [1,2,3,4,5];
array1[0] = "addme";

array[6] = null;

//We shouldn't mix strings, integers, and nulls in arrays, but this isn't a best-practice tutorial.

Remember the JS object syntax and you may start to see a whole new flexible world of objects open up. But it may take a bit.

Answer 3: Ah, yeah... how to merge.

There are seriously (very many) ways to merge two arrays. It depends on exactly what you need. Sorted, Duplicated, Concatenated... there are a few.

Here is the answer!

UPDATE: How to make a beautiful multiple dimensional array.

//Multiple Dimension Array
var array1 = [1,2,3];
var array2 = [3,4];

var arraysinArray = [array1,array2]; //That is it!

Here is the curve again, this could be in an object:

var obj{
   array1:[1,2,3],
   array2:[3,4]
}

JavaScript is powerful stuff, stick with it; it gets good. : )

Hope that helps, All the best! Nash

Answer 2

In this case, think of a JavaScript's object literal {} as being like PHP's associative array.

Given that, an "array of arrays" actually looks like this (using your above desired output):

{public: [["el29t7","3bmGDy"], ["aj19vA", "jO71Ba"]]}

So here we have an object literal with a single property named "public" whose value is a 2-dimensional array.

If we assign the above to a variable we can then push another array onto "public" like this:

var current_data = {public: [["el29t7","3bmGDy"], ["aj19vA", "jO71Ba"]]};

// Using direct property access
current_data.public.push(["t9t9t9", "r4r4r4"]);

// Or using bracket notation
current_data["public"].push(["w2w2w2", "e0e0e0"]);

current_data's value is now:

{public: [
  ["el29t7","3bmGDy"], 
  ["aj19vA", "jO71Ba"], 
  ["t9t9t9", "r4r4r4"], 
  ["w2w2w2", "e0e0e0"]
]}

So now "public" is an array whose length is 4.

current_data.public[0]; // ["el29t7","3bmGDy"]
current_data.public[1]; // ["aj19vA", "jO71Ba"]
current_data.public[2]; // ["t9t9t9", "r4r4r4"]
current_data.public[3]; // ["w2w2w2", "e0e0e0"]

MDN has very good documentation on Array for insight on other functions you might need. https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array

Answer 3

First is an object, that contains array, second is an array.

DEMO showing display output http://jsfiddle.net/GjQCV/

var object={"public":{"0":["el29t7","3bmGDy"]}};
var arr=["aj19vA", "jO71Ba"] ;
/* use object notation to add new property and value which is the array*/
object.public[1]=arr;

Answer 4

It'd be much more natural if {"0": ...} were a true array rather than an object, but anyway:

function maxKey(b) {
    var max;
    for( var key in b )
        var max = key;
    return max;
}
function merge(a,b) {
    for( var key in a ) {
        b[key] = b[key] ? (b[key][maxKey(b)+1]=a[key], b[key]) : a[key];
    }
    return b;
}

Note that this assumes you would insert at the next integer index

Answer 5

1. Arrays are a particular kind of Javascript object
2. JSON is a way of representing Javascript objects (and as such can represent arrays and more)
3. Objects are much more general, and can be simple objects that can be represented as JSON, or can contain functions and prototypes.

So, this is not an array of arrays (you would access items using JSON notation like myobj["0"]):

{"0":["el29t7","3bmGDy"], "1":["aj19vA", "jO71Ba"]}

This is an array of arrays, which means you can use the push method to add an item, and access items using array notation like myobj[0]:

[ ["el29t7","3bmGDy"], ["aj19vA", "jO71Ba"] ]

It seems like the structure you want is something like this:

var myobj = { "public": [ ["key", "value"], ["key", "value"] ] }

Then if you want to add/merge new items, you'd write this:

if (myobj["public"] != null) {
    myobj["public"].push(["newkey", "newval"]);
} else {
    myobj["public"] = ["newkey", "newval"];
}