function getFromAPI(url, callback){
  var obj;
  fetch(url)
    .then(res => res.json())
    .then(data => obj = data)
    .then(() => callback(obj))
 }

getFromAPI('https://jsonplaceholder.typicode.com/posts', getData);

function getData(arrOfObjs){
  var results = "";
  arrOfObjs.forEach( (x) => {
    results += "
 Id: " + x.id + "
"
    Object.keys(x).forEach( (p) => {
        results += "
" + (p + ": " + x[p]) + "
";
    });
    results += "
 
 
"
  })
  results += "";
  document.getElementById("myDiv").innerHTML = results;
}