Fetch API

#review

async function logMovies() {
  const response = await fetch("http://example.com/movies.json");
  const movies = await response.json();
  console.log(movies);
}

The fetch function return Response, which is a http response, which need to turned into json

Supplying request options

// Example POST method implementation:
async function postData(url = "", data = {}) {
  // Default options are marked with *
  const response = await fetch(url, {
    method: "POST", // *GET, POST, PUT, DELETE, etc.
    mode: "cors", // no-cors, *cors, same-origin
    cache: "no-cache", // *default, no-cache, reload, force-cache, only-if-cached
    credentials: "same-origin", // include, *same-origin, omit
    headers: {
      "Content-Type": "application/json",
      // 'Content-Type': 'application/x-www-form-urlencoded',
    },
    redirect: "follow", // manual, *follow, error
    referrerPolicy: "no-referrer", // no-referrer, *no-referrer-when-downgrade, origin, origin-when-cross-origin, same-origin, strict-origin, strict-origin-when-cross-origin, unsafe-url
    body: JSON.stringify(data), // body data type must match "Content-Type" header
  });
  return response.json(); // parses JSON response into native JavaScript objects
}

postData("https://example.com/answer", { answer: 42 }).then((data) => {
  console.log(data); // JSON data parsed by `data.json()` call
});

Aborting a fetch

const controller = new AbortController();
const signal = controller.signal;
const url = "video.mp4";

const downloadBtn = document.querySelector("#download");
const abortBtn = document.querySelector("#abort");

downloadBtn.addEventListener("click", async () => {
  try {
    const response = await fetch(url, { signal });
    console.log("Download complete", response);
  } catch (error) {
    console.error(`Download error: ${error.message}`);
  }
});

abortBtn.addEventListener("click", () => {
  controller.abort();
  console.log("Download aborted");
});

Uploading JSON data and file

async function postJSON(data) {
  try {
    const response = await fetch("https://example.com/profile", {
      method: "POST", // or 'PUT'
      headers: {
        "Content-Type": "application/json",
      },
      body: JSON.stringify(data),
    });

    const result = await response.json();
    console.log("Success:", result);
  } catch (error) {
    console.error("Error:", error);
  }
}

const data = { username: "example" };
postJSON(data);

async function upload(formData) {
  try {
    const response = await fetch("https://example.com/profile/avatar", {
      method: "PUT",
      body: formData,
    });
    const result = await response.json();
    console.log("Success:", result);
  } catch (error) {
    console.error("Error:", error);
  }
}

const formData = new FormData();
const fileField = document.querySelector('input[type="file"]');

formData.append("username", "abc123");
formData.append("avatar", fileField.files[0]);

upload(formData);