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In Javascript array there are items, but when I pass an array to an MVC Controller, list/array is empty

I'm using ajax POST method
to send objects stored in an array to Mvc Controller to save them to a database, but list in my controller is allways empty
while in Javascript there are items in an array.
here is my code with Console.Log.
My controller is called a ProductController, ActionMethod is called Print, so I written:
"Product/Print"
Console.Log showed this:
So there are 3 items!
var print = function () {
console.log(productList);
$.ajax({
type: "POST",
url: "Product/Print",
traditional: true,
data: { productList: JSON.stringify(productList) }
});}
And when Method in my controller is called list is empty as image shows:
Obliviously something is wrong, and I don't know what, I'm trying to figure it out but It's kinda hard, because I thought everything is allright,
I'm new to javascript so probably this is not best approach?
Thanks guys
Cheers

When sending complex data over ajax, you need to send the json stringified version of the js object while specifying the contentType as "application/json". With the Content-Type header, the model binder will be able to read the data from the right place (in this case, the request body) and map to your parameter.
Also you do not need to specify the parameter name in your data(which will create a json string like productList=yourArraySuff and model binder won't be able to deserialize that to your parameter type). Just send the stringified version of your array.
This should work
var productList = [{ code: 'abc' }, { code: 'def' }];
var url = "Product/Print";
$.ajax({
type: "POST",
url: url,
contentType:"application/json",
data: JSON.stringify(productList)
}).done(function(res) {
console.log('result from the call ',res);
}).fail(function(x, a, e) {
alert(e);
});
If your js code is inside the razor view, you can also leverage the Url.Action helper method to generate the correct relative url to the action method.
var url = "#Url.Action("Print","Product)";

How can I iterate this json?

"This" is what I retrieve from a server:
after an ajax call in jQuery:
$.ajax({
type: "POST",
url: URL + "/webservices/WS.asmx/MyFunction",
data: JSON.stringify({ "ID": ID }),
contentType: 'application/json; charset=utf-8',
success: function (json) {
},
error: function (jqxhr, text, error) {
}
});
and I want to iterate the items inside data (which is an array). Tried with:
for (i in json.data) {
var feed = json.data[i];
console.log(feed.message);
}
but it prints nothing. Where am I wrong?

If what you've shown is really what you're getting in your success method, you have an object with a property, d, which contains a JSON string. You can parse it like this:
success: function(response) {
var data = $.parseJSON(response.d).data;
// use the data, which is an array
}
From your comment below:
But why I need to use $.parseJSON? Can't just manage it with the request? dataType for example, but still not works.
You don't need dataType, it would appear the server is returning a correct MIME type and so jQuery is already handling the first level of parsing (deserialization) correctly.
Whatever is sending you the data appears to be sending it double-encoded: First it encodes the array, then creates an object and assigns the array to it as a data property, serializes that object to JSON, then puts that string on a d property of another object, and serializes that. So although jQuery is automatically handling the first parsing (deserializing) step for you, it doesn't know about the need for the second one. I suspect you can fix this at the server level; you might want to post a separate question asking how to do that.
From your further comment:
It retuns from a .NET webservice method. I download the JSON from Facebook, after a call. And I store it inside a json variable. Then I just return it as string. I think webservice serialize that already serialized json, right?
Ah, so that's what's going wrong. You have three options:
Keep doing what you're doing and do the explicit $.parseJSON call above.
Do whatever you need to do in your web method to tell it that you're going to send back raw JSON and it shouldn't encode it; in that case, jQuery will have already parsed it for you by the time you receive it in success and you can drop the parseJSON call.
Parse the string you get from Facebook, then put the resulting array in the structure that your web method returns. Then (again) jQuery will parse it for you and you can use response.d.data directly without further parsing.

As #T.J.Crowder has pointed out your problem is related to the way you serialize your data on your backend, which is not a good practice to send the json as a string, in a real json object.
you should do it like:
success: function (json) {
var jsonObject = JSON.parse(json.d);
//then iterate through it
for(var i=0;i<jsonObject.data.length;i++){
var feed = jsonObject.data[i];
console.log(feed);
}
},
The point is using for(var key in jsonObject.data), is not safe in JavaScript, because additional prototype properties would show up in your keys.

Try using
for (var i in json.d.data) {
var feed = json.d.data[i];
console.log(i+" "+feed);
}
where
i = Key &
feed = value

I assume json is an object not string and already converted to json object. Also used json.d.data not json.data
use var in for loop and print feed not feed.message:
for (var i in json.d.data) {
var feed = json.d.data[i];
console.log(feed);
}
because I can not see {feed:{message:''}} there

Parsing JSON returned via an AJAX POST formating issue

I have a php returning some json in response to a POST request made via an ajax function.
In my php function I format the data like this:
//json return
$return["answers"] = json_encode($result);
echo json_encode($return);
This returns the following string:
answers: "[{"aa":"Purple","0":"Purple","ab":"Blue","1":"Blue","ac":"Red","2":"Red","ad":"Yellow","3":"Yellow"}]"
And this is where I am trying to catch it to use the data:
$.ajax({
type: "POST",
url: "http://ldsmatch.com/pieces/functions/question.functions.php",
dataType : 'JSON',
data: dataString,
success: function(data) {
alert(data.answers[0]["aa"]);
}
});
I've been trying to just alert the data so I can visualize it before setting up the vars I need, but am having some trouble formatting it correctly so it is usable.
If I alert data.answers[0] then it just shows me the first character in the string, which is a bracket [ and if i subsequently change the number it will go through each character in the returned string.
I have tried other variations, such as:
data.answers[0]["aa"] (this returns 'undefined' in the alert)
data.answers["aa"] (this returns 'undefined' in the alert)
data.answers[0] (this returns the first character of the string)
I feel like I'm close, but missing something. Any guidance appreciated.
edit:
thanks for all the suggestions. I removed the second json_encode and was able to parse with data.answers[0].aa

success: function(data) {
var json = $.parseJSON(data);
alert(json.answers[0]["aa"]);
}

Use parseJson like this
var json = $.parseJSON(data);
$(json).each(function(i,val){
$.each(val,function(k,v){
console.log(k+" : "+ v);
});
});

What if you remove double-encoding on PHP side? You've got an object with JSON string instead of object with first property being object itself, or you may explicitly decode "answers" property on client side as it was suggested above.

passing json array ajax

Trying to pass a array using ajax call.
info = [];
info[0] = 'hi';
info[1] = 'hello';
$.ajax({
type: "POST",
data: {info: info, "action": "getPatientRecords"},
url: "/mobiledoc/jsp/ccmr/webPortal/carePlanning/servicePatientmilestoneModal.jsp",
success: function(msg) {
$('.answer').html(msg);
}
});
However when i try to catch it on the server side using :
request.getParameter("info"); //Displays null**
Also, if i wish to send an array of arrays ? is it possible?
I tried using serialize however my IE throws error that serialize : object doesnt support this property i Did include jquery lib.

You can use JSON.stringify(info) to create a JSON representation of the object/array (including an array of arrays). On the server side you should be able to get the string via getParameter and then unserialize it from JSON to create constructs JSP can use.

Yes,It is Possible to send arrays.
var info_to_send = ['hi','hello'];
$.ajax({
type: "POST",
data: {info: info_to_send, "action": "getPatientRecords"},
url: "/mobiledoc/jsp/ccmr/webPortal/carePlanning/servicePatientmilestoneModal.jsp",
success: function(msg) {
$('.answer').html(msg);
}
});

You can only provide strings in a request url.
You could encode the array like so:
info = JSON.stringify(info);
// results in "['hi', 'hello']"
Then send it to the server, also JSON parse on the server.
You will need to go to http://www.json.org/ to get a Java implementation of JSON parsing.

pass array and individual string to php file using ajax call

I try to implement the following code
var flag = new Array();
var name = $("#myselectedset").val();
$.ajax({
type: 'post',
cache: false,
url: 'moveto.php',
data: {'myselectset' : name,
'my_flag' : flag
},
success: function(msg){
$("#statusafter").ajaxComplete(function(){$(this).fadeIn("slow").html(msg)});
}
});
You can see that the name is a single string and the flag is an arry, am I using the right format for passing them throw ajax call, anyone could help me, thanks

It is impossible to pass arrays in a POST request. Only strings.
You will either need to stringify your array, or consider posting as JSON instead.

You should be able to do something quite simple, like replace your "data" property with:
data : JSON.stringify( { myselectset : name, my_flag : flag } )
That will convert the data into a JSON string that you can turn into PHP on the other side, using json_decode($_POST["my_flag"]);
Very important note:
For JSON.stringify to work, there can't be any functions in the array - not even functions that are object methods.
Also, because this is a quick example, make sure that you're testing for null data and all of the rest of the best-practices.