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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)";

Making an AJAX request to an MVC controller and getting the data from the response in js

On button click I am trying to send a product name value that the user enters into a textbox to the server to be modified and then back to the page using AJAX. I am getting into the ChangeName method in the controller but not getting into my success function to alert the new name.
The JS:
$("#changeNameButton").click(function () {
var productName = $("#Name").val();
$.ajax({
url: '/Products/ChangeName/',
type: 'POST',
dataType: 'JSON',
data: {name: productName},
success: successFunc
});
});
function successFunc(data) {
alert(data);
}
The controller:
public string ChangeName(string name)
{
string changedName = ChangeNameHelper(name);
return changedName;
}
If anyone can give recommendations on the proper way to make asynchronous calls to a controller in MVC5/6 this would be great.
My main problem is that I am never getting into the successFunc() on response.

Regarding your comment, if you return just a string MVC will convert that to json.
Now, in your updated code you still call a method inside itself. Please call string changedName = ChangeNameForResult(name); or any function with another name.

Install Newtonsoft.Json via nuget package manager and in your controller do this
Public ActionResult ChangeName(string name)
{
// get your object you want to serialize let's say res
return JsonConvert.SerializeObject(res);
}

I needed to set dataType: 'text' rather than JSON since I am returning a simple string.
dataType is the type of data being returned and contentType is the type of data being sent.

backbone model fetch JSON element by ID

I am using backbone for the first time and I am really struggling to get it to function correctly with a JSON data file.
I have a model Like so:
window.Test = Backbone.Model.extend({
defaults: {
id: null,
name: null,
},
url: function() {
return 'json/test.json/this.id';
},
initialize: function(){
}
});
When a test item is clicked I then try to bring up the details of the pacific model that was clicked by doing
testDetails: function (id) {
var test = new Test();
test.id = id;
test.fetch({ success: function(data) { alert(JSON.stringify(data))}});
},
However this does not work, I am unable to correctly say "get the JSON element with the passed ID"
Can anyone please show me how to correctly structure the models URL to pull the element with the ID.
Thanks

The problem here is that you're treating your JSON data file like a call to a server. That won't work and it's the reason you're getting a 404. If you're accessing a file locally, you have to load the file first. You can do this with jQuery using the .getJSON() method, or if the file's static, just load it into memory with a script block (though you'll probably need to assign a var in the file). Most likely, you'll use jQuery. An example of this can be found here:
Using Jquery to get JSON objects from local file.
If this is an array of JSON, you can load the array into a collection, and use the "at" method to access the particular element by id. If it's entirely JSON, you'll have to create a custom parser.

your url is incorrect for one. you are returning the literal string 'this.id'. you probably want to do something more along the lines of
url: function () {
return 'json/test.json/' + this.id;
}

I would start by fixing your url function:
url: function() {
return 'json/test.json/' + this.get('id');
}
The way you have it now, every fetch request, regardless of the model's id, is going to /json/test.json/test.id

How to pass data from one HTML page to another HTML page using JQuery?

I have two HTML pages that work in a parent-child relationship in this way:
The first one has a button which does two things: First it requests data from the database via an AJAX call. Second it directs the user to the next page with the requested data, which will be handled by JavaScript to populate the second page.
I can already obtain the data via an ajax call and put it in a JSON array:
$.ajax({
type: "POST",
url: get_data_from_database_url,
async:false,
data: params,
success: function(json)
{
json_send_my_data(json);
}
});
function json_send_my_data(json)
{
//pass the json object to the other page and load it
}
I assume that on the second page, a "document ready" JavaScript function can easily handle the capture of the passed JSON object with all the data. The best way to test that it works is for me to use alert("My data: " + json.my_data.first_name); within the document ready function to see if the JSON object has been properly passed.
I simply don't know a trusted true way to do this. I have read the forums and I know the basics of using window.location.url to load the second page, but passing the data is another story altogether.

session cookie may solve your problem.
On the second page you can print directly within the cookies with Server-Script tag or site document.cookie
And in the following section converting Cookies in Json again
How about?

Warning: This will only work for single-page-templates, where each pseudo-page has it's own HTML document.
You can pass data between pages by using the $.mobile.changePage() function manually instead of letting jQuery Mobile call it for your links:
$(document).delegate('.ui-page', 'pageinit', function () {
$(this).find('a').bind('click', function () {
$.mobile.changePage(this.href, {
reloadPage : true,
type : 'post',
data : { myKey : 'myVal' }
});
return false;
});
});
Here is the documentation for this: http://jquerymobile.com/demos/1.1.1/docs/api/methods.html
You can simply store your data in a variable for the next page as well. This is possible because jQuery Mobile pages exist in the same DOM since they are brought into the DOM via AJAX. Here is an answer I posted about this not too long ago: jQuery Moblie: passing parameters and dynamically load the content of a page

Disclaimer: This is terrible, but here goes:
First, you will need this function (I coded this a while back). Details here: http://refactor.blog.com/2012/07/13/porting-javas-getparametermap-functionality-to-pure-javascript/
It converts request parameters to a json representation.
function getParameterMap () {
if (window.location.href.indexOf('?') === (-1)) {
return {};
}
var qparts = window.location.href.split('?')[1].split('&'),
qmap = {};
qparts.map(function (part) {
var kvPair = part.split('='),
key = decodeURIComponent(kvPair[0]),
value = kvPair[1];
//handle params that lack a value: e.g. &delayed=
qmap[key] = (!value) ? '' : decodeURIComponent(value);
});
return qmap;
}
Next, inside your success handler function:
success: function(json) {
//please really convert the server response to a json
//I don't see you instructing jQuery to do that yet!
//handleAs: 'json'
var qstring = '?';
for(key in json) {
qstring += '&' + key + '=' + json[key];
qstring = qstring.substr(1); //removing the first redundant &
}
var urlTarget = 'abc.html';
var urlTargetWithParams = urlTarget + qstring;
//will go to abc.html?key1=value1&key2=value2&key2=value2...
window.location.href = urlTargetWithParams;
}
On the next page, call getParameterMap.
var jsonRebuilt = getParameterMap();
//use jsonRebuilt
Hope this helps (some extra statements are there to make things very obvious). (And remember, this is most likely a wrong way of doing it, as people have pointed out).

Here is my post about communicating between two html pages, it is pure javascript and it uses cookies:
Javascript communication between browser tabs/windows
you could reuse the code there to send messages from one page to another.
The code uses polling to get the data, you could set the polling time for your needs.

You have two options I think.
1) Use cookies - But they have size limitations.
2) Use HTML5 web storage.
The next most secure, reliable and feasible way is to use server side code.

Knockout.js ko.mapping.toJS not refreshing data in my view

I fetch a json object from the server and populate my view. I then change the data, push it back to the server. I then fetch a new copy of the data hoping it will refresh my view with any changes. However that doesn't happen. TIA
$(document).ready(function() {
var customer_id = get_customer_id();
var data = load_model();
contract_model = ko.mapping.fromJS(data,{});
ko.applyBindings(contract_model);
}
function load_model(){
var url = '/ar/contract_json?contract_id='+get_contract_id();
var data = '';
$.ajax({
type:'GET',
url:url,
async:false,
success: function(returningValue){
data = returningValue;
}
});
return data;
}
This initial load works fine. I then do some stuff and change one of the observables and push that data back to server. Server gets the update and then I do a new fetch of the data so that view will refresh (i know i can pass back the new data in one step but this in code i haven't refactored yet).
function refresh_data(contract_model){
var url = '/ar/contract_json?contract_id='+get_contract_id();
$.post(url,function(data){
console.log(data);
ko.mapping.fromJS(contract_model,{},data);
ko.applyBindings(contract_model);
console.log(ko.mapping.toJS(contract_model))
});
}
function refresh_data(contract_model){
var url = '/ar/contract_json?contract_id='+get_contract_id();
$.post(url,function(data){
console.log(data);
ko.mapping.fromJS(contract_model,{},data);
console.log(ko.mapping.toJS(contract_model))
});
}
function push_model(contract_model,refresh){
var url = '/ar/update_contract';
var data = {'contract':ko.mapping.toJSON(contract_model)}
delete data['lines'];
$.post(url,data,function(return_value){
if (refresh){
refresh_data(contract_model);
};
});
}
The console messages all show the new data coming back but my view never updates.

I believe the problem is with the order of parameters you pass into the ko.mapping.fromJS function when you are updating contract_model.
You have:
ko.mapping.fromJS(contract_model,{},data);
you want:
ko.mapping.fromJS(data, {}, contract_model);

#seth.miller's answer is correct. You can also leave out the middle "options" parameter if your contract_model is the same one that was mapped earlier. If there are only two arguments, ko.mapping.fromJS checks if the second argument has a "__ko_mapping__" property. If so, it treats it as a target, otherwise it treats it as an options object.

Based upon #DBueno's observation - for anyone using typescript I strongly recommend commenting out this method signature from your knockout.mapping.d.ts file.
// fromJS(jsObject: any, targetOrOptions: any): any;
Yes - just comment it out.
You'll then get a compile time error if you try to do :
ko.mapping.fromJS(item.data, item.target);
and you can replace it with the much safer
ko.mapping.fromJS(item.data, {}, item.target);
Safer because whether or not item.target has been previously mapped (and therfore would have a __ko_mapping__ property) it will always copy the properties.