移动前端图片压缩上传的实例(3)

//图片上传，将base64的图片转成二进制对象，塞进formdata上传
function upload(basestr, type, $li) {
 var text = window.atob(basestr.split(",")[1]);
 var buffer = new ArrayBuffer(text.length);
 var ubuffer = new Uint8Array(buffer);
 var pecent = 0,
  loop = null;
 for (var i = 0; i < text.length; i++) {
  ubuffer[i] = text.charCodeAt(i);
 }
 var Builder = window.WebKitBlobBuilder || window.MozBlobBuilder;
 var blob;
 if (Builder) {
  var builder = new Builder();
  builder.append(buffer);
  blob = builder.getBlob(type);
 } else {
  blob = new window.Blob([buffer], {
   type: type
  });
 }
 var xhr = new XMLHttpRequest();
 var formdata = new FormData();
 formdata.append('imagefile', blob);
 xhr.open('post', '/cupload');
 xhr.onreadystatechange = function() {
  if (xhr.readyState == 4 && xhr.status == 200) {
   console.log('上传成功：' + xhr.responseText);
   clearInterval(loop);
   //当收到该消息时上传完毕
   $li.find(".progress span").animate({
    'width': "100%"
   }, pecent < 95 ? 200 : 0, function() {
    $(this).html("上传成功");
   });
   $(".pic-list").append('<a href="' + xhr.responseText + '">' + xhr.responseText + '<img src="' + xhr.responseText + '" /></a>')
  }
 };
 //数据发送进度，前50%展示该进度
 xhr.upload.addEventListener('progress', function(e) {
  if (loop) return;
  pecent = ~~(100 * e.loaded / e.total) / 2;
  $li.find(".progress span").css('width', pecent + "%");
  if (pecent == 50) {
   mockProgress();
  }
 }, false);
 //数据后50%用模拟进度
 function mockProgress() {
  if (loop) return;
  loop = setInterval(function() {
   pecent++;
   $li.find(".progress span").css('width', pecent + "%");
   if (pecent == 99) {
    clearInterval(loop);
   }
  }, 100)
 }
 xhr.send(formdata);
}