Axios error in Express middleware - unable to send headers once they have been processed

I can't seem to figure out why my code is not running correctly. While using Axios in my middleware, I am encountering this error message:

Error: Can't set headers after they are sent.

This is the snippet of my code (utilizing Lodash forEach):

app.post('/myApi', function (req, res, next) {
  _.forEach(things, (thing) => {
    axios.post(url, { data: thing })
    .then(()=>{
      // writing data to an excel file
    })
    .then(()=>{
      // need this next to go to next middleware, but it causes the error mentioned above
      next()
    })
  })
})

Even though I specify that I require calling next(), I still face the noted error.

I attempted to make the anonymous Lodash forEach function async and apply an await on the axios.post, however, it didn't resolve the issue. I'm unsure about the exact location where the headers are being sent. What could be causing this problem?

Answer №1

By placing the call to next() inside a _forEach() function, you are triggering next() during each iteration of the loop, resulting in the error you described.

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