Posting Json data on a SAS server is returning an error message Unexpected token '<'

Magued — Fri, 19 Dec 2025 17:37:53 GMT

I am trying to write Json data back to the SAS server. The code creates a temp file but it is empty and in the response.json() I get an error something went wrong: Unexpected token '<' ,",html> <t"... is not valid JSON.

I am including both the JavaScript and the server side code.

JavaScript Code:

const jsonData = {
"name": "value",
"id": 123
};

fetch('YOUR_SAS_SERVER_ENDPOINT_URL', { /* The url is a stored process the code is listed in the
method: 'POST', // Specify the method
headers: {
'Content-Type': 'application/json', // Inform the server the data type
'Accept': 'application/json' // Indicate expected response type (optional)
},
body: JSON.stringify(jsonData) // Convert the JS object to a JSON string
})
.then(response => response.json()) // Process the response (this is where I get the error)
.then(data => console.log('Success:', data))
.catch((error) => {
console.error('Error:', error);
});

Server Side Code;

/* Reference the uploaded/posted JSON data from the input stream */
filename indata temp; /* The file gets created but 0 size and no data*/

/* Use the JSON engine to provide read-only sequential access to JSON data */
libname myjson json fileref=indata;

/* Process the data (e.g., copy to a work dataset and print) */
proc copy inlib=myjson outlib=work;
select alldata; /* 'alldata' is a common default table name created by the JSON engine */
run;

title 'Data Received from JavaScript POST';
proc print data=work.alldata;
run;

/* Clear the libname reference */
libname myjson clear;

/* Optionally, write a JSON response back to the client */
data _null_;
file _webout type='application/json';
put '{ "status": "Data successfully received and processed by SAS" }';
run;
To create the table I am using code similar to:
data _null_;
file _webout;
put '<html>';
put '<head>';

I have tried everything specially on the server side. The Temp file is always 0 size.

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Posting Json data on a SAS server is returning an error message Unexpected token '<'