Javascript message formatting for jit.cellblock values

I'm looking for the correct message format to send data to jit.cellblock in javascript

I've tried various things that get more and more elaborate like:

var celldata_array = {};
var jit_cellblock = this.patcher.getnamed('jit_cellblock');

celldata_array[0] = 1;
celldata_array[1] = 1;
celldata_array[2] = 'a cell value';

jit_cellblock.set(celldata_array);

(which sets the elements of an array as the values in a jit.cellblock cell - 1.row 2.column 3.value)

Is there an obvious way to set a cells value in js?

Michael