Can you use a trailing comma in a JSON object?

Unfortunately the JSON specification does not allow a trailing comma. There are a few browsers that will allow it, but generally you need to worry about all browsers.

In general I try turn the problem around, and add the comma before the actual value, so you end up with code that looks like this:

s.append("[");
for (i = 0; i < 5; ++i) {
  if (i) s.append(","); // add the comma only if this isn't the first entry
  s.appendF("\"%d\"", i);
}
s.append("]");

That extra one line of code in your for loop is hardly expensive…

Another alternative I’ve used when output a structure to JSON from a dictionary of some form is to always append a comma after each entry (as you are doing above) and then add a dummy entry at the end that has not trailing comma (but that is just lazy ;->).

Doesn’t work well with an array unfortunately.

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