Newbie looking to learn nested JSON - arrays

Question

I just started learning JSON and how to convert back and forth between different file types.
If I'm trying to convert a CSV file to JSON
Say if I have a CSV file of people
(First name, Last name, age)
David Chin 40
David Lin 40
David Ping 30
Sandra Lee 25
Sandra Long 45
I can convert that to JSON without any formatting.
How would I go about trying to convert the CSV to a nested JSON?
Hopefully output would look like
{"David":{
"Chin": "40"
"Lin": "40"
"Ping": "30"
},
"Sandra":{
"Lee": "25"
"Long": "45"}
}
Is there any particular code where I can freely format the conversion?
Any help toward the right direction is appreciated or pointers on how to format JSON would also work. I just don't know where I would manipulate to get that format in the output.

Answer 1

Here is a solution using jq
If the file filter.jq contains
[
split("\n") # split string into lines
| [.[0] | split(",")[]] as $headers # split header
| (.[1:][] | split(",")) # split data
| select(length>0) # eliminate blanks
| [ [ $headers, . ] #
| transpose[] # assemble objects
| {key:.[0], value:.[1]} # from keys and values
] | from_entries #
]
| reduce group_by(.First)[][] as $r ( # construct final result
{}
; .[$r.First] = (.[$r.First]//{}) * {($r.Last):$r.Age}
)
and data contains
First,Last,Age
David,Chin,40
David,Lin,40
David,Ping,30
Sandra,Lee,25
Sandra,Long,45
then the command
jq -M -R -s -r -f filter.jq data
will produce the output
{
"David": {
"Chin": "40",
"Lin": "40",
"Ping": "30"
},
"Sandra": {
"Lee": "25",
"Long": "45"
}
}