When manually generating a JSON object or array, it's often easier to leave a trailing comma on the last item in the object or array. For example, code to output from an array of strings might look like (in a C++ like pseudocode): s.append("["); for (i = 0; i < 5; ++i) { s.appendF("\"%d\",", i); } s.append("]"); giving you a string like [0,1,2,3,4,5,] Is this allowed?