<div id="download" >Download CSV</div>

#download { 
  display: inline-block;
  padding: 16px;
  font-family: 'Arial';
  font-size: 20px;
  cursor: pointer; 
  border: 1px solid #ddd;
  border-radius: 5px;
  background: #efefef;
}

const downCsv = document.querySelector("#download");
const csvData = [
  ["id", "name", "message"],
  {
    id: 1,
    name: "Mandy",
    message: "hello\nworld"
  },
  {
    id: 2,
    name: "Mars",
    message: "hello JS"
  }
];

downCsv.addEventListener("click", () => {
  const newData = csvData
    .filter((e, i) => i !== 0)
    .map((e) => {
      return Object.keys(e).reduce((acc, curr) => {
        return { ...acc, ...{ [curr]: '"' + e[curr] + '"' } };
      }, {});
    });
  console.log(newData)
  exportFile(newData);
});

const exportFile = ( rows, fileTitle) => {

    const jsonObject = JSON.stringify(rows);
    const csv = '\ufeff' + convertToCSV(jsonObject); // support Chinese

    const blob = new Blob([csv], { type: 'text/csv;charset=utf-8;' });

    const link = document.createElement('a');
    const url = URL.createObjectURL(blob);
    link.setAttribute('href', url);
    link.setAttribute('download', fileTitle || 'data.csv');
    link.style.visibility = 'hidden';
    document.body.appendChild(link);
    link.click();
    document.body.removeChild(link);
  }

  const toCsv = objArray => {
    const array =
      typeof objArray !== 'object' ? JSON.parse(objArray) : objArray;
    
    const newData = array.map(e => {
      console.log('array', e)
      const str = Object.entries(e).reduce((arr, [k,v], i) => {
        return [...arr, v];
      }, []);
      return str.join(',') + '\r\n';
    })
    
    return newData.join('');
  }

  /* CSV: convert json to json */
  const convertToCSV = (objArray) => {
    const array =
      typeof objArray !== 'object' ? JSON.parse(objArray) : objArray;
    let str = '';
    console.log('aa', array);

    for (let i = 0; i < array.length; i++) {
      let line = '';
      Object.entries(array[i]).forEach(([key, value]) => {
        if (line !== '') {
          line += ',';
        }
        line += value;
      });
      str += line + '\r\n';
      console.log('TT', str)
    }
    console.log('bb', str);
    
    return str;
  }