// window.addEventListener('paste', ... or

document.onpaste = function (event) {

  // use event.originalEvent.clipboard for newer chrome versions

  var clipboardData = event.clipboardData  ||  event.originalEvent.clipboardData;

  var items = clipboardData.items;

  console.log(JSON.stringify(items)); // will give you the mime types

  // find pasted image among pasted items

  var blob;

  for (var i = 0; i < items.length; i++) {

    if (items[i].type.indexOf("image") === 0) {

      blob = items[i].getAsFile();

    }

  }

  // load image if there is a pasted image

  if (blob !== null) {

    var reader = new FileReader();

    reader.onload = function(event) {

      console.log(event.target.result); // data url!

    };

    reader.readAsDataURL(blob);

  }

}