Getting parse error while fetching text file content in JQuery

Question

I am trying to fetch data from text file which resides on server. I have access of that location and able to see content when I put URL in browser tab. I am trying to make AJAX call and get file content, but I am getting Error: Uncaught SyntaxError: Unexpected identifier

Code

    function logResults(json){
  console.log(json);
}

$.ajax({
  url: u,
  dataType: "jsonp",
  jsonpCallback: "logResults"
});

on console,

I tried below code too, but same result,

     $.ajax({
   type: 'GET',
   url: u,
   crossDomain: true,
   dataType: 'jsonp',
   async: false,
   headers: {
     "Access-Control-Allow-Origin": "*"
     },
   success: function(succ) {
     console.log("Success: ", succ)
   },
   error: function(err) {
     console.log("Error: ", err)
   }
 });

This code is always going into error block.

does the server actually return `jsonp` - or are you desperately trying all the usual "tricks" to circumvent CORS issues ... CORS is controlled **by the server** ... adding `"Access-Control-Allow-Origin": "*"` shows that you don't know that — Bravo, Apr 27 '22 at 10:57

Quentin · Accepted Answer · 2022-04-27T12:46:48.890

You said:

dataType: "jsonp",

But the URL is responding with:

Deployment automatically finished…

Which is not JSONP, it is plain text.

You get the error when it tries to execute the plain text as JSONP.

Don't put wrong information in the dataType field.

async: false,

That's deprecated. Don't use it. It's also pointless since you are using callbacks.

It's also incompatible with JSONP so it is ignored (until you remove the incorrect dataType).

crossDomain: true,

This has no effect unless you are making a:

non-JSONP request
to the same origin
which gets redirected to a different origin

… which is very rare.

headers: {
    "Access-Control-Allow-Origin": "*"
 },

Access-Control-Allow-Origin is a response header. It doesn't belong the request. Trying to add it to the request will cause extra problems as it will make the request preflighted.

(At least, that would be the case if you hadn't said dataType: 'jsonp' because adding request headers is incompatible with JSONP).

All you need on the client

The only code you need on the client is:

function logResults(result){
   console.log(result);
}

$.ajax({
    url: u,
    success: logResults
});

The server you are requesting the data from will need to use CORS to grant you permission to access it if it is a cross-origin request.

score 0 · Answer 2 · answered Apr 27 '22 at 10:59

0

It is because you have added dataType as jsonp, so that it will try to parse the response to JSON and if the response is not a JSON it will throw error.

answered Apr 27 '22 at 10:59

Nikhil Unni

739
5
12

`it will try to parse the response to JSON` -actually it won't ... it will load it as a ` – Bravo Apr 27 '22 at 11:22
1

it will fail - since JSON isn't valid javascript (though, if the data is an array, it may not throw an error since it's possible to have a statement in javascript like `[]` – Bravo Apr 27 '22 at 11:31
Understood bro, it expects a script right – Nikhil Unni Apr 27 '22 at 11:31
it actually expects something like `function xyz() { return something_that_is_valid_in_javascript }` and the underlying code will call `result = xyz()` ... that's when the error would happen if the JSON response was parsable as javascript, since there was no function – Bravo Apr 27 '22 at 11:34
1

It expects `name_of_callback_function_passed_in_url({some: "data", that: "is usually an object literal", here: true });` and jQuery (or whatever JSONP library) will have created `window.name_of_callback_function_passed_in_url` when it made the request. In the OP's version, they are overriding the auto function generation with `logResults` which isn't good for handling parallel requests. – Quentin Apr 27 '22 at 13:44

Getting parse error while fetching text file content in JQuery

2 Answers2

All you need on the client