Response: json() static method

{{APIRef("Fetch API")}}{{AvailableInWorkers}}

The json() static method of the {{domxref("Response")}} interface returns a Response that contains the provided JSON data as body, and a {{HTTPHeader("Content-Type")}} header which is set to application/json. The response status, status message, and additional headers can also be set.

The method makes it easy to create Response objects for returning JSON encoded data. Service workers, for example, intercept fetch requests made by a browser, and might use json() to construct a Response from cached JSON data to return to the main thread. The json() method can also be used in server code to return JSON data for single page applications, and any other applications where a JSON response is expected.

Syntax

Response.json(data)
Response.json(data, options)

Parameters

• data
  • : The JSON data to be used as the response body.
• options {{optional_inline}}
  • : An options object containing settings for the response, including the status code, status text, and headers. This is the same as the options parameter of the {{domxref("Response.Response", "Response()")}} constructor.
    • status
      • : The status code for the response, such as 200.
    • statusText
      • : The status message associated with the status code. For a status of 200 this might be OK.
    • headers
      • : Any headers you want to add to your response, contained within a {{domxref("Headers")}} object or object literal of {{jsxref("String")}} key/value pairs (see HTTP headers for a reference).

Return value

A {{domxref("Response")}} object.

Exceptions

• {{jsxref("TypeError")}}
  • : Thrown if data cannot be converted to a JSON string. This might happen if the data is a JavaScript object that has method, or that has a circular reference, or if the passed object is undefined.

Examples

Response with JSON data

This live example shows how you can create a JSON response object, and logs the newly created object for inspection (the logging code is hidden as it is not relevant).

<pre id="log"></pre>

const logElement = document.getElementById("log");
function log(text) {
  logElement.innerText += `${text}\n`;
}

async function logResponse(response) {
  const responseText = await response.text();
  log(`body: ${responseText}`);
  response.headers.forEach((header) => log(`header: ${header}`));
  log(`status: ${response.status}`);
  log(`statusText: ${response.statusText}`);
  log(`type: ${response.type}`);
  log(`url: ${response.url}`);
  log(`ok: ${response.ok}`);
  log(`redirected: ${response.redirected}`);
  log(`bodyUsed: ${response.bodyUsed}`);
}

The code below creates a Response object with JSON body { my: "data" } and header set to application/json.

const jsonResponse = Response.json({ my: "data" });
logResponse(jsonResponse);

The object has the following properties. Note the body and header are set as expected, and that the default status is set to 200.

{{EmbedLiveSample('Response with JSON data','100%', '170')}}

Response with JSON data and options

This example shows how you can create a JSON response object with status and statusText options.

<pre id="log"></pre>

const logElement = document.getElementById("log");
function log(text) {
  logElement.innerText += `${text}\n`;
}

async function logResponse(response) {
  const responseText = await response.text();
  log(`body: ${responseText}`);
  response.headers.forEach((header) => log(`header: ${header}`));
  log(`status: ${response.status}`);
  log(`statusText: ${response.statusText}`);
  log(`type: ${response.type}`);
  log(`url: ${response.url}`);
  log(`ok: ${response.ok}`);
  log(`redirected: ${response.redirected}`);
  log(`bodyUsed: ${response.bodyUsed}`);
}

The code below creates a Response object with JSON body { some: "data", more: "information" } and header set to application/json. It also sets the status to 307 and sets the appropriate status text ("Temporary Redirect").

const jsonResponse = Response.json(
  { some: "data", more: "information" },
  { status: 307, statusText: "Temporary Redirect" },
);
logResponse(jsonResponse);

The object has the following properties, which are set as expected. Note that the ok property of the response changed to false as the status value is not in the range of 200 to 299.

{{EmbedLiveSample('Response with JSON data and options','100%', '170')}}

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• Service Worker API