Searching prime numbers by using a web worker

<!DOCTYPE html>
<html>
  <head>
    <link rel="stylesheet" href="style.css">
  </head>

  <body class="blocking">
    <h1>Searching prime numbers by using a web worker</h1>
    <label for="limit">Limit
      <input id="limit" type="number" value="10000">
    </label>
    
    <button class="search">start search</button>
    
    <div class="prime-numbers"></div>
    
    <script src="script.js"></script>
  </body>

</html>

(function(w, d) {

  d.querySelector('.search').addEventListener('click', function() {
    
    // Create a new worker with the worker script
    var worker = new Worker('worker.js');
    
    // Adding an event listener to receive postMessage events from the worker
    worker.addEventListener('message', function(e) {
      var primeElement = d.createElement('span');
      primeElement.classList.add('prime');
      primeElement.textContent = e.data.prime;
      
      d.querySelector('.prime-numbers').appendChild(primeElement);
    });
    
    // To start the worker we need to post an initial message where we also pass
    // in parameters to the worker.
    worker.postMessage({
      limit: d.querySelector('#limit').value
    });
    
  });

}(window, document));

@import url("http://fonts.googleapis.com/css?family=Open+Sans:400,300,600");

*, *:before, *:after {
  box-sizing: border-box;
  -webkit-appearance: none;
  -moz-appearance: none;
  -ms-appearance: none;
  appearance: none;
}

*:before, *:after {
  content: '';
  clear: both;
}

.blocking {
  font-family: "Open Sans", sans-serif;
  color: rgba(0, 0, 0, 0.8);
  font-size: 1rem;
  text-align: center;
  
  h1 {
    text-transform: uppercase;
    text-align: center;
  }
  
  label {
    display: block;
    text-align: center;
    
    input {
      width: 10ch;
      padding: 0.3em;
      border: 1px solid rgba(0, 0, 0, 0.2);
      border-radius: 3px;
      background: transparent;
      font-family: "Open Sans", sans-serif;
      font-size: 1em;
      color: rgba(0, 0, 0, 0.8);
    }
  }
  
  button {
    display: inline-block;
    margin: 2em 0 3em 0;
    padding: 1em 2em;
    border: 3px solid rgba(0, 0, 0, 0.2);
    border-radius: 3px;
    background: transparent;
    font-family: "Open Sans", sans-serif;
    text-transform: uppercase;
    font-weight: 200;
    font-size: 1em;
    color: rgba(0, 0, 0, 0.5);
    
    transition: all 0.3s ease-out;
    
    &:hover {
      outline: none;
      border-color: #000064;
      color: rgba(0, 0, 0, 0.8);
    }
    
    &:focus {
      outline: none;
    }
  }
  
  .prime {
    display: inline-block;
    margin: 0.5em;
    width: 3em;
    height: 3em;
    background-color: #000064;
    line-height: 3em;
    color: white;
    border-radius: 3em;
  }
}

(function(s) {
  
  function findPrimeNumbers(limit) {
    var isPrime,
        i,
        j;

    for(i = 1; i < limit; i++) {
      isPrime = true;

      for(j = 2; j < i; j++) {
        if(i % j === 0) {
          isPrime = false;
        } 
      }

      if(isPrime) {
        // Instead of accessing the DOM (which is not possible in workers anyway)
        // we will fire a postMessage event and the host is listening for it.
        s.postMessage({
          prime: i
        });
      }
    }
  }

  // Here is the entry point for the worker. It will start the thread by 
  // receiving a postMessage from a Web Worker host.
  s.addEventListener('message', function(e) {
    findPrimeNumbers(e.data.limit);
  });

}(self));