title: How can I read the xlsx-file using JS on client
body: <p>I can get some properties a xlsx-file such its name, size, type, but I can't read data of this file in base64-coding:</p>
  
  <pre><code>function onFilesSelect(e) {
  
      var files = e.target.files; // xlsx-file
      console.log(files[0]);
  
      for(var i = 0; i &lt; files.length; i++) {    
          var file = files[i];
  
          var data = [file.name, file.type, file.size];
          var reader = new FileReader();
  
          reader.onload = (function (file, data) {
              return function (e) {
                  console.log(e.target.result); 
              };
          })(file, data);
  
          var list = reader.readAsBinaryString(file);
          //var list = reader.readAsArrayBuffer(file);
          //var list = reader.readAsText(file, 'utf-8');
          //var list = reader.readAsDataURL(file);
          console.log(list); // wrong data
      };
  };
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/9XccX.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9XccX.jpg" alt="screenshot of console"></a></p>
  
  <p>I had used different metods readAsArrayBuffer(), readAsText(),  readAsDataURL() but I can't read the xlsx-data. 
  I don't want use server side I'm trying use only client side (<a href="https://dev.w3.org/2009/dap/file-system/pub/FileSystem/" rel="nofollow noreferrer">https://dev.w3.org/2009/dap/file-system/pub/FileSystem/</a>)
  Can somebody help me? </p>