docs.sheetjs.com/docz/static/systemjs/main.js

/* sheetjs (C) 2013-present SheetJS -- https://sheetjs.com */
/*jshint browser:true */
/*global XLSX */
var XLSX = require('xlsx');

var global_wb;

var process_wb = (function() {
  var OUT = document.getElementById('out');
  var HTMLOUT = document.getElementById('htmlout');

  var get_format = (function() {
    var radios = document.getElementsByName( "format" );
    return function() {
      for(var i = 0; i < radios.length; ++i) if(radios[i].checked || radios.length === 1) return radios[i].value;
    };
  })();

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

  var to_csv = function to_csv(workbook) {
    var result = [];
    workbook.SheetNames.forEach(function(sheetName) {
      var csv = XLSX.utils.sheet_to_csv(workbook.Sheets[sheetName]);
      if(csv.length){
        result.push("SHEET: " + sheetName);
        result.push("");
        result.push(csv);
      }
    });
    return result.join("\n");
  };

  var to_fmla = function to_fmla(workbook) {
    var result = [];
    workbook.SheetNames.forEach(function(sheetName) {
      var formulae = XLSX.utils.get_formulae(workbook.Sheets[sheetName]);
      if(formulae.length){
        result.push("SHEET: " + sheetName);
        result.push("");
        result.push(formulae.join("\n"));
      }
    });
    return result.join("\n");
  };

  var to_html = function to_html(workbook) {
    HTMLOUT.innerHTML = "";
    workbook.SheetNames.forEach(function(sheetName) {
      var htmlstr = XLSX.write(workbook, {sheet:sheetName, type:'string', bookType:'html'});
      HTMLOUT.innerHTML += htmlstr;
    });
    return "";
  };

  return function process_wb(wb) {
    global_wb = wb;
    var output = "";
    switch(get_format()) {
      case "form": output = to_fmla(wb); break;
      case "html": output = to_html(wb); break;
      case "json": output = to_json(wb); break;
      default: output = to_csv(wb);
    }
    if(OUT.innerText === undefined) OUT.textContent = output;
    else OUT.innerText = output;
    if(typeof console !== 'undefined') console.log("output", new Date());
  };
})();

var setfmt = window.setfmt = function setfmt() { if(global_wb) process_wb(global_wb); };

var b64it = window.b64it = (function() {
  var tarea = document.getElementById('b64data');
  return function b64it() {
    if(typeof console !== 'undefined') console.log("onload", new Date());
    var wb = XLSX.read(tarea.value, {type:'base64', WTF:false});
    process_wb(wb);
  };
})();

var do_file = (function() {
  return function do_file(files) {
    var f = files[0];
    var reader = new FileReader();
    reader.onload = function(e) {
      if(typeof console !== 'undefined') console.log("onload", new Date());
      var data = e.target.result;
      data = new Uint8Array(data);
      process_wb(XLSX.read(data, {type: 'array'}));
    };
    reader.readAsArrayBuffer(f);
  };
})();

(function() {
  var drop = document.getElementById('drop');
  if(!drop.addEventListener) return;

  function handleDrop(e) {
    e.stopPropagation();
    e.preventDefault();
    do_file(e.dataTransfer.files);
  }

  function handleDragover(e) {
    e.stopPropagation();
    e.preventDefault();
    e.dataTransfer.dropEffect = 'copy';
  }

  drop.addEventListener('dragenter', handleDragover, false);
  drop.addEventListener('dragover', handleDragover, false);
  drop.addEventListener('drop', handleDrop, false);
})();

(function() {
  var xlf = document.getElementById('xlf');
  if(!xlf.addEventListener) return;
  function handleFile(e) { do_file(e.target.files); }
  xlf.addEventListener('change', handleFile, false);
})();