npm install xlsx
or
yarn add xlsx

<input type="file" id="uploadExcel" multiple />

window.document.getElementdById("uploadExcel").addEventListener("change", function(e){
    let fileList = e.target.files;
})

let reader = new FileReader();

reader.onload = function(e){
    let data = e.target.result;
};
reader.readAsDataURL(file);

XLSX.read(data, { type: type });

let wb;  // 讀取完成的數(shù)據(jù)
let rABS = false; // 是否將文件讀取為二進(jìn)制字符串
document.getElementById("excel").addEventListener("change",function (e) {
  if(!e.target.files) return;
  var f = e.target.files[0];
  var reader = new FileReader();
  reader.onload = function(e) {
    var data = e.target.result;
      if(rABS) {
        wb = XLSX.read(btoa(fixdata(data)), {type: 'base64'});//手動(dòng)轉(zhuǎn)化
      } 
      else {
       wb = XLSX.read(data, {type: 'binary'});
      }
      //wb.SheetNames[0]是獲取Sheets中第一個(gè)Sheet的名字
      //wb.Sheets[Sheet名]獲取第一個(gè)Sheet的數(shù)據(jù)
    document.getElementById("demo").innerHTML= JSON.stringify( XLSX.utils.sheet_to_json(wb.Sheets[wb.SheetNames[0]]) );
  };
  if(rABS) {reader.readAsArrayBuffer(f);} 
  else {reader.readAsBinaryString(f);}
  });
      
function fixdata(data) { //文件流轉(zhuǎn)BinaryString
  var o = "",
  l = 0,
  w = 10240;
  for(; l < data.byteLength / w; ++l) 
    o += String.fromCharCode.apply(null, new Uint8Array(data.slice(l * w, l * w + w)));
    o += String.fromCharCode.apply(null, new Uint8Array(data.slice(l * w)));
  return o;
}

sheet1:{
    !merge: [
    {
        e: { c: 5, r: 0 },
      s: { c: 0, r: 0 }  // 表示A1到F1單元格合并
    },
    {
        e: { c: 5, r: 9 },
      s: { c: 0, r: 9 }  // 表示A10到F10單元格合并
    }
  ]
}

// 讀取 excel文件
function outputWorkbook(workbook) {    
  var sheetNames = workbook.SheetNames; // 工作表名稱集合
  sheetNames.forEach(name => {        
    var worksheet = Workbook.Sheets[name]; // 只能通過工作表名稱來獲取指定工作表
    for(var key in worksheet) {            // v是讀取單元格的原始值
        console.log(key, key[0] === '!' ? worksheet[key] : worksheet[key].v);
    }
   });
}