Javascript onclick почему не работает? ('onclick' of null")

window.onload = function() { 
  var shareBtn = document.getElementById('#share'); 
 
  shareBtn.onclick = function() { 
    var x = document.getElementById("#social"); 
    if (x.style.display === "none") { 
      x.style.display = "block"; 
    } else { 
      x.style.display = "none"; 
    } 
  } 
};

.social-network { 
  display: none; 
  width: 50px; 
  height: 50px; 
  background: red 
}

<a href="#" id="share" class="product__share-btn">Share it!</a> 
<div id="social" class="social-network"></div>