JSON parsing error syntax error unexpected end of input

user_1794925 0
Viewed 518063

I got the following piece of code

function pushJsonData(productName) {
    $.ajax({
        url: "/knockout/SaveProduct",
        type: "POST",
        contentType: "application/json",
        dataType: "json",
        data: " { \"Name\" : \"AA\" } ",
        async: false,
        success: function () {
            loadJsonData();   
        },
        error: function (jqXHR, textStatus, errorThrown) {
          alert(textStatus + " in pushJsonData: " + errorThrown + " " + jqXHR);
        }
    });
}

Notice that I hard coded the data value. The data get pushed into the database fine. However, I keep getting the error

parsing error syntax error unexpected end of input

I am sure my data is in correct JSON syntax. When I checked with on Network of Chrome inspector the saveProduct request showed the data is correct.

{ "Name": "AA" }

This POST request did not have response. So I am clueless as to where the parse error was coming from. I tried using FireFox browser. the same thing happened.

Can anyone give some idea as to what is wrong?

Thanks,

P.S. Here is the controller code

namespace MvcApplJSON.Controllers
{
    public class KnockoutController : Controller
    {
        //
        // GET: /Knockout/

        public ActionResult Index()
        {
            return View();
        }

        [HttpGet]
        public JsonResult GetProductList()
        {
            var model = new List<Product>();
            try
            {
                using (var db = new KOEntities())
                {
                    var product = from p in db.Products orderby p.Name select p;
                    model = product.ToList();
                }
            }
            catch (Exception ex)
            { throw ex; }
            return Json(model, JsonRequestBehavior.AllowGet);
        }
        [HttpPost]
        public void SaveProduct (Product product)
        {
            using (var db = new KOEntities())
            {
                db.Products.Add(new Product { Name = product.Name, DateCreated = DateTime.Now });
                db.SaveChanges();
            }
        }
    }
}
asp.net-mvc-4 knockout.js jquery json ajax
10 Answers

Don't Return Empty Json

In My Case I was returning Empty Json String in .Net Core Web API Project.

So I Changed My Code

From

 return Ok();

To

 return Ok("Done");

It seems you have to return some string or object.

Hope this helps.

user_22186970

May be it will be useful.

The method parameter name should be the same like it has JSON

It will work fine

C#

public ActionResult GetMTypes(int id)

JS

 var params = { id: modelId  };
                 var url = '@Url.Action("GetMTypes", "MaintenanceTypes")';
                 $.ajax({
                     type: "POST",
                     url: url,
                     contentType: "application/json; charset=utf-8",
                     dataType: "json",
                     data: JSON.stringify(params),

It will NOT work fine

C#

public ActionResult GetMTypes(int modelId)

JS

 var params = { id: modelId  };
                 var url = '@Url.Action("GetMTypes", "MaintenanceTypes")';
                 $.ajax({
                     type: "POST",
                     url: url,
                     contentType: "application/json; charset=utf-8",
                     dataType: "json",
                     data: JSON.stringify(params),
user_1969190

spoiler: possible Server Side Problem

Here is what i've found, my code expected the responce from my server, when the server returned just 200 code, it wasnt enough herefrom json parser thrown the error error unexpected end of input

fetch(url, {
        method: 'POST',
        body: JSON.stringify(json),
        headers: {
          'Content-Type': 'application/json'
        }
      })
        .then(res => res.json()) // here is my code waites the responce from the server
        .then((res) => {
          toastr.success('Created Type is sent successfully');
        })
        .catch(err => {
          console.log('Type send failed', err);
          toastr.warning('Type send failed');
        })
user_92774530

I've had the same error parsing a string containing \n into JSON. The solution was to use string.replace('\n','\\n')

user_25165510

This error occurs on an empty JSON file reading.

To avoid this error in NodeJS I'm checking the file's size:

const { size } = fs.statSync(JSON_FILE);
const content = size ? JSON.parse(fs.readFileSync(JSON_FILE)) : DEFAULT_VALUE;
user_61082110
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