Edit in JSFiddle

[].forEach.call(document.querySelectorAll('.bShadow-1, .bShadow-2h, .bShadow-3'), function(node) {
  var bsh = getComputedStyle(node).boxShadow;
  node.style.boxShadow = "inset " + bsh;
});
<a href="#" class="bShadow-1" title="">bShadow-1</a>