Fetch API (function)

The most useful, high-level part of the Fetch API is the fetch() function. In its simplest form it takes a URL and returns a promise that resolves to the response. The response is captured as a Response object.

// Fetch sample
saveCourse(id: number, changes: any): any {
  return of(fetch(`/api/courses/${id}`)
    .then(result => {
      console.log(result);
    })
    .catch(err => {
      console.error(err);
    }), {
    method: 'PUT',
    body: JSON.stringify(changes),
    headers: {
      'content-type': 'application/json'
    }
  });
}

Submitting some parameters, it would look like this:

fetch("http://www.example.org/submit.php", {
  method: "POST",
  headers: {
    "Content-Type": "application/x-www-form-urlencoded"
  },
  body: "firstName=Nikhil&favColor=blue&password=easytoguess"
}).then(function(res) {
  if (res.ok) {
    alert("Perfect! Your settings are saved.");
  } else if (res.status == 401) {
    alert("Oops! You are not authorized.");
  }
}, function(e) {
  alert("Error submitting form!");
});

For more information about the fetch method, please check this link https://hacks.mozilla.org/2015/03/this-api-is-so-fetching/