JSFiddle - React, Tailwind, and code Playground

HTML

<label>Enter your hashrate:</label>
<input type="text" id="userHashrateInput">
    
<input type="submit" id="submit" onclick="userHashrate();">
        
<p><span id='display'></span></p>

JavaScript

(function() {
    document.getElementById("submit").onclick = function() {
        makeRequest('https://blockchain.info/q/getdifficulty', function(response) {
            var totalHashrateNum = Number(response); // convert the API response to a number to do math on
            var userHashrate = document.getElementById('userHashrateInput').value;
            var userHashrateNum = Number(userHashrate);
            var timeToFindBlock = (((((totalHashrateNum * Math.pow(2, 32)) / (userHashrate*1000000000))/60)/60)/24);
            document.getElementById('display').innerHTML ="It will take you " + timeToFindBlock + " days to find a block!";
        });
    };

  function makeRequest(url, success) {
    var httpRequest;
    if (window.XMLHttpRequest) { // Mozilla, Safari, ...
      httpRequest = new XMLHttpRequest();
    } else if (window.ActiveXObject) { // IE
      try {
        httpRequest = new ActiveXObject("Msxml2.XMLHTTP");
      } 
      catch (e) {
        try {
          httpRequest = new ActiveXObject("Microsoft.XMLHTTP");
        } 
        catch (e) {}
      }
    }

    if (!httpRequest) {
      alert('Giving up :( Cannot create an XMLHTTP instance');
      return false;
    }
      httpRequest.onreadystatechange = function() {
          if (httpRequest.readyState === 4) {
              if (httpRequest.status === 200) {
                  success(httpRequest.responseText);
              } else {
                  alert('Error getting response');
              }
          }
      };
    httpRequest.open('GET', url);
    httpRequest.send();
  }
})();