How to globally replace strings in lines NOT starting with a certain pattern

Question

I want to globally replace the string foo with the string bar, using sed. This should only be done for lines which do NOT start with the string ##Input.

I can\'t get

Answer 1

An ugly answer for an ugly request (i.e. they get what they asked for):

echo \{
for file in *.json; do
    sed -n '/^[\{\}]/! s/\([^\,]\)$/\1,/; /^[\{\}]/!p' $file
done
echo \{