screenshot.js

var e = document.createElement('script');
e.type = 'text/javascript';
e.charset='UTF-8';
e.src = 'https://cdnjs.cloudflare.com/ajax/libs/html2canvas/0.4.1/html2canvas.js';
document.body.appendChild(e);
function repFun() {
  if (typeof html2canvas !== 'function') {
    setTimeout(repFun);
  } else {
    html2canvas(document.body, {
      onrendered: function(canvas) {
        var imageType = 'image/png';
        var image = canvas.toDataURL(imageType);
        var bin = atob(image.replace(/^.*,/, ''));
        var buffer = new Uint8Array(bin.length);
        for (var i = 0; i < bin.length; i++) {
          buffer[i] = bin.charCodeAt(i);
        }
        var blob = new Blob([buffer.buffer], {
          type: imageType
        });
        var blobUrl = URL.createObjectURL(blob);
        window.location = blobUrl;
      }
    });
  }
};
repFun();