Javascript Upload to self

How can i upload a file and get its contents in javas开发者_如何学Gocript. For example, i want to upload an mp3 and play it in the html5 audio tag without having it on the server. Is this possible?

You can read local files from JavaScript with the File API. Only Firefox >= 3.6 implements it I think and it's still a Working Draft.

Demo (if you try it in Firefox, it only supports .wav and .ogg audio files):

<input id="input" type="file">
<button onclick="play()">play</button>
<script>
  function play() {
    var file = document.getElementById("input").files[0];
    var reader = new FileReader();
    reader.onload = function(e) {
      var audio = new Audio(e.target.result);
      audio.play();
    }
    reader.readAsDataURL(file);
  }
</script>

See also developer.mozilla.org/en/Using_files_from_web_applications

When uploading files, javascript cannot (without plug-in support) gain access to the file. To do what you are asking for, you must actually upload the file to the server and then have your javascript be a client to your server to retrieve the file, and then play it.