Find images data-src to base64 image or blob

// USE: <img src="img/placeholderimg.jpg" data-src="http://www.website.com/img/pic_mountain.jpg">
// call function: findimg();

imgtobase64.js

// USE: <img src="img/placeholderimg.jpg" data-src="http://www.website.com/img/pic_mountain.jpg">
function findimg() {
  var imgEl = document.getElementsByTagName('img');

  for (var i = 0; i < imgEl.length; i++) {
    if (imgEl[i].getAttribute('data-src')) {

      var imgdatasrc = imgEl[i].getAttribute('data-src');

      //imgToBlob(imgEl[i], imgdatasrc); // use this for blob 
      imgToBase64(imgEl[i], imgdatasrc);

    }
  }
}


function imgToBase64(selector, url, onSuccess, onError) {
  var xhr = new XMLHttpRequest();

  xhr.responseType = "arraybuffer";
  xhr.open("GET", url);

  xhr.onload = function() {
    var base64, binary, bytes, mediaType;

    bytes = new Uint8Array(xhr.response);
    //NOTE String.fromCharCode.apply(String, ...
    //may cause "Maximum call stack size exceeded"
    binary = [].map.call(bytes, function(byte) {
      return String.fromCharCode(byte);
    }).join('');
    mediaType = xhr.getResponseHeader('content-type');
    base64 = [
      'data:',
      mediaType ? mediaType + ';' : '',
      'base64,',
      btoa(binary)
    ].join('');
    //onSuccess(base64);
    console.log(base64)
    selector.src = base64;
  };
  xhr.onerror = onError;
  xhr.send();
} // end function imgToBase64


function imgToBlob(selector, imgdatasrc) {

  // Simulate a call to Dropbox or other service that can
  // return an image as an ArrayBuffer.
  var xhr = new XMLHttpRequest();

  //alert(imgurl);
  // Use JSFiddle logo as a sample image to avoid complicating
  // this example with cross-domain issues.
  xhr.open("GET", imgdatasrc, true);

  // Ask for the result as an ArrayBuffer.
  xhr.responseType = "arraybuffer";

  xhr.onerror = function(e) {
    selector.src = "img/user.png";
    //return false

  };

  xhr.onload = function(e) {
    // Obtain a blob: URL for the image data.
    var arrayBufferView = new Uint8Array(this.response);
    var blob = new Blob([arrayBufferView], {
      type: "image/jpeg"
    });
    var urlCreator = window.URL || window.webkitURL;
    var blobimg = urlCreator.createObjectURL(blob);

    //selector.setAttribute("src", imgdatasrc);
    selector.src = blobimg;
  };

  xhr.send();

}