Returning column value

When i do:

grid.setProperty("selection/index", index); // Select a row

And after that I want to read out de first column of that row with:
var array = grid.getProperty("selection/values");
var columnValue = grid.getProperty("data/value", array[0], 0);
The columnValue returns 0!

But if I manually (in my browser) select a row and retrieve the columnValue the same way as above, it returns the proper value.

How do I get a columnValue of the row that was selected by code?