Question

I am following Html5rocks tutorial

http://www.html5rocks.com/en/tutorials/file/dndfiles/

and I am trying to use readAsArrayBuffer instead of readAsBinaryString in slicing a file example (because I want to read gif header to find file resolution). But I am stuck because evt.target.result (while using readAsBinaryString it is a string)

any ideas?

EDIT : Code

reader.onloadend = function(evt) 

{

  if (evt.target.readyState == FileReader.DONE) { // DONE == 2
    document.getElementById('byte_content').textContent = evt.target.result;
    console.log(evt.target.result.byteLenght)
    document.getElementById('byte_range').textContent = 
        ['Read bytes: ', start + 1, ' - ', stop + 1,
         ' of ', file.size, ' byte file'].join('');
  }
};

if (file.webkitSlice) {
  var blob = file.webkitSlice(start, stop + 1);
} else if (file.mozSlice) {
  var blob = file.mozSlice(start, stop + 1);
}
reader.readAsArrayBuffer(blob);
}

so in Firefox 13 I get on screen : [object ArrayBuffer]

and on console log : undefined

while in Chromium 18 I get on console : Uncaught TypeError: Cannot read property ‘byteLenght’ of null

Answer 1

There is a typing mistake in:

console.log(evt.target.result.byteLenght)

byteLenght should be byteLength