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Editorial Team
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Asked: 2026-06-15T07:06:17+00:00

What techniques are used to load a file (ASCII or Binary) into a variable

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What techniques are used to load a file (ASCII or Binary) into a variable (var file = “text”;) in JavaScript?

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1 Answer

  1. Editorial Team

    If you want to use the new HTML5 way this is how I did it… keep in mind that I made a method called File() and this is not a true HTML5 method its a wrapper to it… this might be changed in the future so beware (maybe rename it).

    HTML:

      <html>
    <body>
      <input type="file" id="files" name="file"/> 
      <button onclick="load()">Load File</button><br /><br />
      <div id="content"></div>
      <script>
        function load() {
          var fileObj = document.getElementById("files");
          var fp = new File(fileObj);
          fp.read(callback);
        }
        function callback(text) {
          var content = document.getElementById("content");
          content.innerHTML = text;
        }
      </script>
    </body>
  </html>

    JavaScript:

    function File(name) {
  this.name = document.getElementById(name) ? document.getElementById(name).files : name.files ? name.files : name;
}

// Reads the file from the browser 
File.prototype.read = function(callback) {
  var files = this.name;
  if (!files.length) {
    alert('Please select a file!?');
    return;
  }
  var file = files[0];
  var reader = new FileReader();
  reader.onloadend = function(evt) {
    if (evt.target.readyState == FileReader.DONE) { // DONE == 2
      callback(evt.target.result);
    }
  };
  var data = file.slice(0, file.size);
  reader.readAsBinaryString(data);
}
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