Converts a 2D array to a comma-separated values (CSV) string.
- Use 
Array.prototype.map()andArray.prototype.join()to combine individual 1D arrays (rows) into strings, using the provideddelimiter. - Use 
Array.prototype.join()to combine all rows into a CSV string, separating each row with a newline (\n). - Omit the second argument, 
delimiter, to use a default delimiter of,. 
代码实现
const arrayToCSV = (arr, delimiter = ',') =>
  arr
    .map(v =>
      v.map(x => (isNaN(x) ? `"${x.replace(/"/g, '""')}"` : x)).join(delimiter)
    )
    .join('\n');
arrayToCSV([['a', 'b'], ['c', 'd']]); // '"a","b"\n"c","d"'
arrayToCSV([['a', 'b'], ['c', 'd']], ';'); // '"a";"b"\n"c";"d"'
arrayToCSV([['a', '"b" great'], ['c', 3.1415]]);
// '"a","""b"" great"\n"c",3.1415'