Reactjs - 无法对来自 react-dropzone 的文件进行 base64 编码

Question

I am using react-dropzone to handle file upload on my website. When successfully loading a file, the dropzone triggers the following callback:

onDrop: function (acceptedFiles, rejectedFiles) {
  myFile = acceptedFiles[0];
  console.log('Accepted files: ', myFile);
}

I would like to base64 encode this file. When doing :

var base64data = Base64.encode(myFile)
console.log("base64 data: ", base64data) // => base64 data: W29iamVjdCBGaWxlXQ==W29iamVjdCBGaWxlXQ==

Regardless of file uploaded, it always prints out the same string.

Am I missing something ? I need to base64 encode this file (always images)

Answer 1

This JS Bin is a working example of converting a File to base64: http://jsbin.com/piqiqecuxo/1/edit?js,console,output . The main addition seems to be reading the file using a FileReader , where FileReader.readAsDataURL() returns a base64 encoded string

document.getElementById('button').addEventListener('click', function() {
  var files = document.getElementById('file').files;
  if (files.length > 0) {
    getBase64(files[0]);
  }
});

function getBase64(file) {
   var reader = new FileReader();
   reader.readAsDataURL(file);
   reader.onload = function () {
     console.log(reader.result);
   };
   reader.onerror = function (error) {
     console.log('Error: ', error);
   };
}

Answer 2

If you want it in a neat method that works with async / await, you can do it this way

const getBase64 = async (file: Blob): Promise<string | undefined> => {
  var reader = new FileReader();
  reader.readAsDataURL(file as Blob);

  return new Promise((reslove, reject) => {
    reader.onload = () => reslove(reader.result as any);
    reader.onerror = (error) => reject(error);
  })
}