AJAX

XHR(XML HTTP Request)

var btn = document.querySelector("button");

var display = document.querySelector("#price");

var currency = "USD";

btn.addEventListener("click", function(){

var XHR = new XMLHttpRequest();                                                               fetch(url)

    XHR.onreadystatechange = function(){                                                        .then(function(response){

      if(XHR.readyState == 4 && XHR.status == 200){                                          return response.json()

      var data = JSON.parse(XHR.responseText);                                                   })

      var price = data.bpi[currency].rate;                                                            .then(function(data){

       display.innerText= price + " " = currency;                                                   console.log(data.bpi.EUR.rate);

    }                                                                                                           });

  }

  XHR.open("GET", "https://api.coindesk.com/v1/bpi/currentprice.json");

  XHR.send();

})