title: Javascript export csv file name
body: <p>I have html table (table id='testTable') and a button in html:</p>
  
  <pre><code> &lt;button id="btnExport" onclick="javascript:xport.toCSV('testTable');"&gt;CSV&lt;/button&gt;
  </code></pre>
  
  <p>and javascript code:</p>
  
  <pre><code>toCSV: function(tableId, filename) {
  var date=new Date();
  this._filename = (typeof filename === 'undefined') ? tableId :      filename;
  // Generate our CSV string from out HTML Table
  var csv = this._tableToCSV(document.getElementById(tableId));
  // Create a CSV Blob
  var blob = new Blob([csv], { type: "text/csv" });
  
  // Determine which approach to take for the download
  if (navigator.msSaveOrOpenBlob) {
    // Works for Internet Explorer and Microsoft Edge
    navigator.msSaveOrOpenBlob(blob, this._filename + ".csv");
  } else {      
    this._downloadAnchor(URL.createObjectURL(blob), 'csv');      
  }
  }
  
  
  _tableToCSV: function(table) {
  // We'll be co-opting `slice` to create arrays
  var slice = Array.prototype.slice;
  
  return slice
    .call(table.rows)
    .map(function(row) {
      return slice
        .call(row.cells)
        .map(function(cell) {
          return '"t"'.replace("t", cell.textContent);
        })
        .join(",");
    })
    .join("\r\n");
  }
  </code></pre>
  
  <p>i want to change the filename to current date how can I do that?</p>