Home/ Questions/''error [err_http_headers_sent]: cannot set headers after they are sent to the client'' - simple solution when encountering the error
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daxmann
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Asked: 2022-06-26T05:45:12+00:00 In:

”error [err_http_headers_sent]: cannot set headers after they are sent to the client” – simple solution when encountering the error

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I get the “error [err_http_headers_sent]: cannot set headers after they are sent to the client” issue when I am trying to use Express to make Some APIs in NodeJs:

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
  at new NodeError (node:internal/errors:371:5)
  at ServerResponse.setHeader (node:_http_outgoing:576:11)

Here is my program:

app.post("/login", (req, res) => {

 if (!req.body.username) {
  res.status(400).json({
   status_code: 0,
   error_msg: "Require Params Missing",
  });
 }

 res.status(200).json({
  status_code: 1,
  data: req.body,
 });

});

What’s causing it, and how can it be resolved in the ”error [err_http_headers_sent]: cannot set headers after they are sent to the client”?

 

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2 Answers

  1. Best Answer
    Expert

    The cause: I think this error happens because your function won’t stop while res.status(400).json is running.

    The execution of a function is halted when a return statement is used in the function body. A given value is returned to the function caller if specified.

    Solution: You can fix this error by using return statement.

    In your request handler function, add a return statement as the following:

    app.post("/login", (req, res) => {

 if (!req.body.username) {
  return res.status(400).json({
   status_code: 0,
   error_msg: "Require Params Missing",
  });
 }

 res.status(200).json({
  status_code: 1,
  data: req.body,
 });

});
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  2. Expert
    • 2

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