var str = ‘阪井泉水‘;

  //console.log(encodeURI(str));
  //console.log(btoa(encodeURI(str)));

  //console.log(atob(btoa(encodeURI(str))));
  //console.log(decodeURI(atob(btoa(encodeURI(str)))));


  //字符串轉base64
  function encode(str){
    // 對字符串進行編碼
    var encode = encodeURI(str);
    // 對編碼的字符串轉化base64
    var
 
 base64 = btoa(encode);
    return base64;
  }

  // base64轉字符串
  function decode(base64){
      // 對base64轉編碼
      var decode = atob(base64);
      // 編碼轉字符串
      var str = decodeURI(decode);
      return str;
  }

  console.log(encode(str));
  console.log(decode(encode(str)));

js中字符串轉base64和base64轉字符串