title: R datatable rowCallback with DT
body: <p>I am trying to perform two distinct formatting operations on a datatable object using the DT and magrittr packages. One uses the helper function formatRound() and the other is passed in as JavaScript to a rowCallback option in the datatable function.</p>
  
  <p>When I run either of the formatting operations individually the datatable renders with the expected formatting. However, when I run both together the datatable renders blank but I do not get an error.</p>
  
  <p>This code shows the behavior I am describing.</p>
  
  <pre><code>library(magrittr)
  library(DT)
  
  df = data.frame(matrix(rnorm(20), nrow=10))
  
  datatable(
    data = df
  ) %&gt;%
    formatRound(c("X1", "X2"), 1)
  
  #table renders as expected
  
  datatable(
    data = df,
    options = list(
      rowCallback = JS("
       function( row, data, index ) {
         if ( index &gt; 2 ) {
          $(row).css('background-color', '#EDEDED');
         }
         else if ( index &gt; 0 ) {
          $(row).css('background-color', '#DEDEDE');
         }
         else {
          $(row).css('background-color', '#D3D3D3');
         }
       }"
      )
    )
  )
  
  #table renders as expected
  
  datatable(
    data = df,
    options = list(
      rowCallback = JS("
       function( row, data, index ) {
        if ( index &gt; 2 ) {
          $(row).css('background-color', '#EDEDED');
        }
        else if ( index &gt; 0 ) {
          $(row).css('background-color', '#DEDEDE');
        }
        else {
          $(row).css('background-color', '#D3D3D3');
        }
       }"
      )
    )
  ) %&gt;%
    formatRound(c("X1", "X2"), 1)
  
  #table renders as blank but with no error returned
  </code></pre>