Read a csv or excel (xlsx) file with just javascript and html?

Is it possible to read a excel xlsx or csv, preferably xlsx, using just JavaScript and html. All the solutions (sheetsJS, d3{d3 uses the Fetch API}) I have found require a webserver. I understand I can get a simple webserver using web server for chrome or python or node.js. Futhermore, I understand I can run chrome with certain flags, but I would like to not do this because of security concerns. I am building a demo for someone who is not web savvy and would like to avoid doing this.

my file structure is very simple :

TestFolder
| index.html
| js/
    | test.js
| data/
    | test.xlsx
| css/
    | test.css

I simply need to read the xlsx and then display that data in html page.

Answer

I’ve added a simple example that accepts Excel or CSV files (current example accepts a single file), uses the SheetJS library to parse the Excel file type, convert the data to JSON and logs the contents to the console.

This should be more than enough to complete your demo. Hope this helps!

var file = document.getElementById('docpicker')
var viewer = document.getElementById('dataviewer')
file.addEventListener('change', importFile);

function importFile(evt) {
  var f = evt.target.files[0];

  if (f) {
    var r = new FileReader();
    r.onload = e => {
      var contents = processExcel(e.target.result);
      console.log(contents)
    }
    r.readAsBinaryString(f);
  } else {
    console.log("Failed to load file");
  }
}

function processExcel(data) {
  var workbook = XLSX.read(data, {
    type: 'binary'
  });

  var firstSheet = workbook.SheetNames[0];
  var data = to_json(workbook);
  return data
};

function to_json(workbook) {
  var result = {};
  workbook.SheetNames.forEach(function(sheetName) {
    var roa = XLSX.utils.sheet_to_json(workbook.Sheets[sheetName], {
      header: 1
    });
    if (roa.length) result[sheetName] = roa;
  });
  return JSON.stringify(result, 2, 2);
};

<script src="https://cdnjs.cloudflare.com/ajax/libs/xlsx/0.14.3/xlsx.full.min.js"></script>
<label for="avatar">Choose an Excel or CSV file:</label>
<input type="file" id="docpicker" accept=".csv,application/vnd.ms-excel,.xlt,application/vnd.ms-excel,.xla,application/vnd.ms-excel,.xlsx,application/vnd.openxmlformats-officedocument.spreadsheetml.sheet,.xltx,application/vnd.openxmlformats-officedocument.spreadsheetml.template,.xlsm,application/vnd.ms-excel.sheet.macroEnabled.12,.xltm,application/vnd.ms-excel.template.macroEnabled.12,.xlam,application/vnd.ms-excel.addin.macroEnabled.12,.xlsb,application/vnd.ms-excel.sheet.binary.macroEnabled.12">

<div id="dataviewer">