Very often, we need to include HTTP headers in the request. We can specify these in the options object in a headers property:

fetch("https://jsonplaceholder.typicode.com/posts", {
 method: "POST",
 headers: {
  "Content-Type": "application/json",
  Authorization: "bearer some-bearer-token"
  },
  body: JSON.stringify({
    title: "Interesting post",
    body: "This is an interesting post about ...",
    userId: 1
  })
})
  .then(response => {
    console.log(response.status); 
    return response.json();
  })
  .then(data => console.log(data));

Request headers can be used in this way for any HTTP method and not just an HTTP POST. For example, we can use this for a GET request as follows:

fetch("https://jsonplaceholder.typicode.com/posts/1", {
  headers: {
    "Content-Type": "application/json",
    Authorization: "bearer some-bearer-token"
  }
}).then(...);

So, that's how to use fetch to post data to a REST API. In the next section, we'll look at changing data.