React fetch call status no content

You are not returning the promise returned by response.json(), so your promise chain is broken and undefined is given as argument to the last function.

Add the return keyword and it will work as expected.

fetch("http://localhost:5000/api/signin", {
  method: "post",
  headers: {
    "Content-Type": "application/json",
    Authorization: "this-can-be-anything"
  },
  body: JSON.stringify({
    email: this.state.email,
    password: this.state.password
  })
})
  .then(response => {
    return response.json();
  })
  .then(data => {
    console.log(data);
  });

This issue occurs because you are not returning anything from

.then(response => {
  console.log(response);
  response.json();
})

If you add curly braces to an arrow function; then you need to add an explicit return. So change it to either:

.then(() => response.json())

or

.then(() => {
  return response.json();
})

And it should work.

Looks like you need to return the Promise returned by .json()

This can be cleaned up a bit using the modern ES7 feature of async/await avoiding the ubiquitous callback hell

const loginUser = async () => {

  const response = await fetch("http://localhost:5000/api/signin", {
    method: "post",
    headers: {
      "Content-Type": "application/json",
      Authorization: "this-can-be-anything"
    },
    body: JSON.stringify({
      email: this.state.email,
      password: this.state.password
    })
  })

  const data = await response.json();

  console.log('[data]', data);

  return data;
}