将flie转blob

function fileChange(file) {
  let reader = new FileReader();
  let rs = reader.readAsArrayBuffer(file);
  let blob = null;
  reader.onload = (e) => {
    if (typeof e.target.result === 'object') {
      blob = new Blob([e.target.result])
    } else {
      blob = e.target.result
    }
    console.log(Object.prototype.toString.call(blob));
  }
}

将blob转base64

function blobToDataURI(blob, callback) {
  var reader = new FileReader();
  reader.readAsDataURL(blob);
  reader.onload = function(e) {
    callback(e.target.result);
  };
}

将base64转换为文件

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);
  }
  return new File([u8arr], filename, { type: mime });
}