When using implicit headers (not calling response.writeHead() explicitly), this property controls the status code that will be sent to the client when the headers get flushed.

response.statusCode = 404;

After response header was sent to the client, this property indicates the status code which was sent out.

When using implicit headers (not calling response.writeHead() explicitly), this property controls the status message that will be sent to the client when the headers get flushed. If this is left as undefined then the standard message for the status code will be used.

response.statusMessage = 'Not found';

After response header was sent to the client, this property indicates the status message which was sent out.

If set to true, Node.js will check whether the Content-Length header value and the size of the body, in bytes, are equal. Mismatching the Content-Length header value will result in an Error being thrown, identified by code:``'ERR_HTTP_CONTENT_LENGTH_MISMATCH'.

Sends an HTTP/1.1 100 Continue message to the client, indicating that the request body should be sent. See the 'checkContinue' event on Server.

Sends an HTTP/1.1 103 Early Hints message to the client with a Link header, indicating that the user agent can preload/preconnect the linked resources. The hints is an object containing the values of headers to be sent with early hints message. The optional callback argument will be called when the response message has been written.

Example

const earlyHintsLink = '</styles.css>; rel=preload; as=style';
response.writeEarlyHints({
  'link': earlyHintsLink,
});

const earlyHintsLinks = [
  '</styles.css>; rel=preload; as=style',
  '</scripts.js>; rel=preload; as=script',
];
response.writeEarlyHints({
  'link': earlyHintsLinks,
  'x-trace-id': 'id for diagnostics',
});

const earlyHintsCallback = () => console.log('early hints message sent');
response.writeEarlyHints({
  'link': earlyHintsLinks,
}, earlyHintsCallback);

Sends a response header to the request. The status code is a 3-digit HTTP status code, like 404. The last argument, headers, are the response headers. Optionally one can give a human-readable statusMessage as the second argument.

headers may be an Array where the keys and values are in the same list. It is not a list of tuples. So, the even-numbered offsets are key values, and the odd-numbered offsets are the associated values. The array is in the same format as request.rawHeaders.

Returns a reference to the ServerResponse, so that calls can be chained.

const body = 'hello world';
response
  .writeHead(200, {
    'Content-Length': Buffer.byteLength(body),
    'Content-Type': 'text/plain',
  })
  .end(body);

This method must only be called once on a message and it must be called before response.end() is called.

If response.write() or response.end() are called before calling this, the implicit/mutable headers will be calculated and call this function.

When headers have been set with response.setHeader(), they will be merged with any headers passed to response.writeHead(), with the headers passed to response.writeHead() given precedence.

If this method is called and response.setHeader() has not been called, it will directly write the supplied header values onto the network channel without caching internally, and the response.getHeader() on the header will not yield the expected result. If progressive population of headers is desired with potential future retrieval and modification, use response.setHeader() instead.

// Returns content-type = text/plain
const server = http.createServer((req, res) => {
  res.setHeader('Content-Type', 'text/html');
  res.setHeader('X-Foo', 'bar');
  res.writeHead(200, { 'Content-Type': 'text/plain' });
  res.end('ok');
});

Content-Length is read in bytes, not characters. Use Buffer.byteLength() to determine the length of the body in bytes. Node.js will check whether Content-Length and the length of the body which has been transmitted are equal or not.

Attempting to set a header field name or value that contains invalid characters will result in a [Error][] being thrown.

Sends a HTTP/1.1 102 Processing message to the client, indicating that the request body should be sent.