JavaScript 实现 Ajax 请求二进制图片流

function getBinary(url, args, success) {
  var xmlhttp = new XMLHttpRequest();
  var data = eval(args);
  var i = 0;
  for (var key in data) {
    if (i++ === 0) {
      url += '?' + key + "=" + data[key];
    } else {
      url += '&' + key + "=" + data[key];
    }
  }
  xmlhttp.open("GET", url, true);
  xmlhttp.responseType = "blob";
  xmlhttp.onload = function () {
    success(this.response);
  };
  xmlhttp.send();
}

function submit() {
  getBinary("/request/qrCode", {'data': $('#str').val()},
    function (data) {
      var img = $('#qrcode');
      window.URL.revokeObjectURL(img.src);
      $('#qrcode').attr('src', window.URL.createObjectURL(data));
    })
}