Convert input=file to byte array

I try to convert a file that i get through an input file into a byte[]. I tried with a FileReader, but i must miss something :

var bytes = [];
var reader = new FileReader();
reader.onload = function () {
   bytes = reader.result;
};
reader.readAsArrayBuffer(myFile);

But in the end, my bytes var doesn't content a byte array.

I saw this post : Getting byte array through input type = file but it doesn't ends with a byte[], and readAsBinaryString() is deprecated

What do i miss?

Faced a similar problem and its true the 'reader.result' doesn't end up as 'byte[]'. So I have cast it to Uint8Array object. This too is not a perfect 'byte[]' ,so I had to create a 'byte[]' from it. Here is my solution to this problem and it worked well for me.

var reader = new FileReader();
var fileByteArray = [];
reader.readAsArrayBuffer(myFile);
reader.onloadend = function (evt) {
    if (evt.target.readyState == FileReader.DONE) {
       var arrayBuffer = evt.target.result,
           array = new Uint8Array(arrayBuffer);
       for (var i = 0; i < array.length; i++) {
           fileByteArray.push(array[i]);
        }
    }
}

'fileByteArray' is what you are looking for. Saw the comments and seems you did the same, still wanted to share the approach.

Seems to me you just want to get files into an array? How about these functions - one where you can read it as text, another as a base64 byte string, and if you really want the readAsArrayBuffer array buffer output, I've included that, too:

document.getElementById("myBtn").addEventListener("click", function() {
  uploadFile3();
}); 

var fileByteArray = [];

function uploadFile1(){
  var files = myInput.files[0];
  var reader = new FileReader();
  reader.onload = processFile(files);
  reader.readAsText(files); 
}

function uploadFile2(){
  var files = document.querySelector('input').files[0];
  var reader = new FileReader();
  reader.onload = processFile(files);
  reader.readAsDataURL(files); 
}

function uploadFile3(){
  var files = myInput.files[0];
  var reader = new FileReader();
  reader.onload = processFile(files);
  reader.readAsArrayBuffer(files); 
}

function processFile(theFile){
  return function(e) { 
    var theBytes = e.target.result; //.split('base64,')[1]; // use with uploadFile2
    fileByteArray.push(theBytes);
    document.getElementById('file').innerText = '';
    for (var i=0; i<fileByteArray.length; i++) {
        document.getElementById('file').innerText += fileByteArray[i];
    }
  }
}

<input id="myInput" type="file">    
<button id="myBtn">Try it</button>
<span id="file"></span>

来源：https://stackoverflow.com/questions/37134433/convert-input-file-to-byte-array

标签

javascript

filereader