SOURCE

    function download  ()  {
    //   const content = { 'hello': "wor2ld"};
    //   const fileName = 'sd.json';
    //   let blob = new Blob(
    //       [[JSON.stringify(content, null, 2)]], 
    //       { type : 'application/json' });
      const fileName = 'sd.xlsx';
      let blob = new Blob([s2ab('2asda')], { 
        //   type: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;charset=utf-8'
          type: "application/vnd.ms-excel"
          })
      
      const url = window.URL.createObjectURL(blob); 
      //URL.createObjectURL(object)表示生成一个File对象或Blob对象
      let a = document.createElement("a"); 
      //设置一个隐藏的a标签，href为输出流，设置download
      a.style.display = "none";
      a.href = url;
      // a.setAttribute("download", fileName); 
      a.download = fileName;
      //指示浏览器下载url,而不是导航到它；因此将提示用户将其保存为本地文件
      document.body.appendChild(a);
      debugger;
      a.click();
     
      window.URL.revokeObjectURL(url);
       document.body.removeChild(a);
    }


function s2ab(s) {
  var buf = new ArrayBuffer(s.length);
  var view = new Uint8Array(buf);
  for (var i=0; i!=s.length; ++i) view[i] = s.charCodeAt(i) & 0xFF;
  return buf;
}

<p onclick="download()">
下载
</p>