fetch js response header code example

Example 1: how to use fetch() javascript

//Most API's will only allow you to fetch on their website.
//This means you couldn't run this code in the console on 
// google.com because:
// 		1. Google demands the fetch request be from https
// 		2. open-notify's API blocks the request outside of their website

fetch('http://api.open-notify.org/astros.json')
.then(function(response) {
  return response.json();
})
.then(function(json) {
  console.log(json)
});

// Here is another example. A method (function) that 
// grabs Game of Thrones books from an API ...

function fetchBooks() {
  return fetch('https://anapioficeandfire.com/api/books')
  .then(resp => resp.json())
  .then(json => renderBooks(json));
}

function renderBooks(json) {
  const main = document.querySelector('main')
  json.forEach(book => {
    const h2 = document.createElement('h2')
    h2.innerHTML = `
${book.name}
`
    main.appendChild(h2)
  })
}

document.addEventListener('DOMContentLoaded', function() {
  fetchBooks()
})

Example 2: fetch get request

// 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
  });