Likes Example

schema of the basic addEventListener, fetch() and callback:

const EMPTY_HEART = '♡'
const FULL_HEART = '♥'

let heartStates = {
  "♡": "♥",
  "♥": "♡"
};

let articleHearts = document.querySelectorAll(".like");

function likeCallback(e) {
  let heart = e.target;
  fetch("/bogus_url")
    .then(function(serverMessage){
       heart.innerText = heartStates[heart.innerText];
    })
    .catch(function(error) {
      console.log('there was an error)
    });
}

for (let glyph of articleHearts) {
  glyph.addEventListener("click", likeCallback);
}

Original Example