Any JQ built-in function returning index of element in JSON array?
to_entries should work perfectly.
jq -n '["a","b","c"] | to_entries'will produce
[{"key":0,"value":"a"},{"key":1,"value":"b"},{"key":2,"value":"c"}]
There are two robust (i.e., that work in jq 1.3, 1.4 and 1.5) ways to iterate through an array with an index: one is to use keys[] (which works on arrays as well as objects), and the other using range/2. These two approaches can be illustrated as follows, assuming $a is an array:
($a | keys[]) as $i | [$i, $a[$i]] range(0; $a | length) as $i | [$i, $a[$i]]Or more succinctly:
$a | keys[] as $i | [$i, .[$i]]$a | range(0;length) as $i | [$i, .[$i]]If your jq has keys_unsorted, you might wish to use it instead.
(index/1 is probably not what is needed here.)