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Today, the editor will share with you the relevant knowledge points about how to use setHeader and writeHead in Node. The content is detailed and the logic is clear. I believe most people still know too much about this knowledge, so share this article for your reference. I hope you can get something after reading this article. Let's take a look.

SetHeader

Parameters.

Response.setHeader (name, value) copy code

Name attribute

Value attribute value

Return http.ServerResponse. Return response object.

Action

Set a single property for the response header.

Be careful

You can only set properties one by one.

Setting a property repeatedly replaces the previous setting

Setting a property field name or value that contains invalid characters will cause a TypeError to be thrown

Example

Reponse.setHeader ('Content-Type',' text/html') reponse.setHeader ('Set-Cookie', [' type=ninja', 'language=javascript'])

Set a property repeatedly

/ / return content-type = text/html1reponse.setHeader ('Content-Type',' text/html') reponse.setHeader ('Content-Type',' text/html1')

WriteHead

Parameters.

Response.writeHead (statusCode, [statusMessage], [headers])

StatusCode http status code

StatusMessage status information (optional)

Headers | attribute object or array (optional)

Return http.ServerResponse. Return response object.

Action

Have the same effect as setHeader

Be careful

You can set multiple properties, and setHeader can only set one.

Can only be called once

Must be called before response.end ()

Setting a property field name or value that contains invalid characters will cause a TypeError to be thrown

Example

Because writeHead returns a ServerResponse object, we can make chained calls

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

The Content-Length here is in bytes, not characters. Buffer.byteLength () is used to determine the length of the text.

Nodejs does not check whether the length of the Content-Length and the transmitted text are the same.

Use both setHeader and writeHead// to return content-type = text/plainconst server = http.createServer ((req, res) = > {res.setHeader ('Content-Type',' text/html'); res.setHeader ('Xmuri Foodies,' bar'); res.writeHead (200,{ 'Content-Type':' text/plain'}); res.end ('ok');})

WriteHead has a higher priority than setHeader, and writeHead can only be called once, so when calling, consider which headers don't change often before calling writeHead.

If setHeader has been called to set the header, it will be passed to writeHead merge

If this method is called and response.setHeader () has not been called, the supplied header value is written directly to the network channel and is not cached internally. Response.getHeader () on the header does not produce the expected results. If you need to gradually populate the header and potentially retrieve and modify it in the future, use response.setHeader () instead.

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