Construct json through jq tool in shell script loop - json

Question

json can be created using the following command.
jq -n \
--arg v1 "Value1" \
--arg v2 "Value2" \
'{k1: "$v1", k2:$v2'}
But when my key is mutable, how should I loop? For example, the script I execute is
test.sh k1=v1 k2=v2 k3=v3
test.sh is as follows
index=1
while ((index <= "$#")); do
data_i_key=$(echo ${!index} | awk -F "=" '{print $1}')
data_i_value=$(echo ${!index} | awk -F "=" '{print $2}')
let index++
JSON_STRING=$(jq -n \
--arg value "$data_i_value" \
'{'"$data_i_key"': $value'})
echo $JSON_STRING
The above print result is
{ "K3": "V3" }
if I replace it with
JSON_STRING+=$(jq -n \
--arg val_value "$dataValue" \
'{'"$data_i_key"': $val_value'})
The print result is
{ "k1": "v1" }{ "k2": "v2" }{ "K3": "V3" }
The above two methods have not achieved the goal, do you have a good way to deal with it? My desired output is
{ "k1": "v1" , "k2": "v2" ,"K3": "V3" }
hope you can help me.

Answer 1

I'd suggest a totally different, but simpler, approach:
for kv; do
echo "$kv" | jq -R './"=" | {key:first,value:last}'
done | jq -s 'from_entries'
It builds {key: …, value: …} objects from your positional parameters (splitting them by the equal sign) and then slurping all those objects in a second jq process, converting them into a single object via from_entries.
Alternatively, using -n (--null-input), --args and then accessing via $ARGS.positional. This avoids the loop and the second jq call altogether.
jq -n '$ARGS.positional | map(./"=" | {key:first,value:last}) | from_entries' --args "$#"
If your values can contain = themselves, you have to join all but the first value of the array:
jq -n '$ARGS.positional
| map(./"=" | {key:first,value:.[1:]|join("=")})
| from_entries' --args "$#"

Answer 2

Use parentheses around the key expression to have it evaluated:
jq -n --arg k1 "Key1" --arg v1 "Value1" '{($k1): $v1}'
{
"Key1": "Value1"
}

Answer 3

Perhaps this, which will handle an arbitrary number of key=value arguments:
#!/usr/bin/env bash
args=()
for arg; do
IFS="=" read -r k v <<<"$arg"
args+=("$k" "$v")
done
jq -n --args '
$ARGS.positional as $a
| reduce range(0; $a | length; 2) as $i ({}; .[$a[$i]] = $a[$i + 1])
' "${args[#]}"
Produces:
$ ./test.sh k1=v1 k2=v2 k3=v3
{
"k1": "v1",
"k2": "v2",
"k3": "v3"
}