JavaScript create and download CSV

jsCsvDownload

    //columns is array of string values, or something falsy
    //rows is 2d array with inner arrays comprised of cell values (strings)
    //columns array will have same length as each member of rows array 
    $scope.downloadCsv = function(columns, rows, filenameWithoutExtension) {
        let separator = "\n";

        // join(',') + "\n";
        // const header = columnsArr.join(',') + "\r\n";
        const header = columns.join(',') + separator;

        const body = rows.map(function(row) {
            return row.join(',');
        })
            .join(separator);
        const data = header + body;

        // blob allows largest file size of available options, but limit varies by browser
        const blob = new Blob([data], {type: 'text/csv'});
        const url = window.URL.createObjectURL(blob);

        // attach a hidden anchor to the dom and emit click event
        // this technique is necessary for firefox
        const a = document.createElement('a');
        a.setAttribute('hidden','');
        a.setAttribute('href', url);
        a.setAttribute('download', filenameWithoutExtension + '.csv');
        document.body.appendChild(a);
        a.click();
        document.body.removeChild(a);
    }