base64,blod,fileObject的相互转换

　//文件路径 转 fileObject
 1 try{
   let response = await fetch(tempFilePath);
   if(response.ok){
     let myBlob = await response.blob();
     // console.log(myBlob);
     tampFileObj = new File([myBlob],"cs" + new Date().getTime());
     console.log(myFile);
   }else{
     11    }
}catch(err){
                
}

//base64转fileObject
function dataURLtoFile(dataurl, filename) {
  var arr = dataurl.split(',');
  var mime = arr[0].match(/:(.*?);/)[1];
  var bstr = atob(arr[1]);
  var n = bstr.length; 
  var u8arr = new Uint8Array(n);
  while(n--){
      u8arr[n] = bstr.charCodeAt(n);
  }
  //转换成file对象
  return new File([u8arr], filename, {type:mime});
}