Combine two JSON arrays in a single file using jq

Question

I have a JSON file with two arrays. I'd like to combine the arrays into a single array of objects, each of which contains an element from each of the original arrays.

JSON input looks like this:

{ "en": [ "E1", "E2", "E3", "E4" ], "fr": [ "F1", "F2", "F3", "F4" ] }

Desired output:

[ { "en":"E1", "fr":"F1"}, { "en":"E2", "fr":"F2"}, { "en":"E3", "fr":"F3"}, { "en":"E4", "fr":"F4"} ]

No matter what I try I can't tame jq into delivering this. The closest I have come is using the filter . | {en:.en[],fr:.fr[]} which gives me every possible pairing of the arrays as follows:

{ "en": "E1", "fr": "F1" } { "en": "E1", "fr": "F2" } { "en": "E1", "fr": "F3" } { "en": "E1", "fr": "F4" } { "en": "E2", "fr": "F1" } { "en": "E2", "fr": "F2" } { "en": "E2", "fr": "F3" } { "en": "E2", "fr": "F4" } { "en": "E3", "fr": "F1" } { "en": "E3", "fr": "F2" } { "en": "E3", "fr": "F3" } { "en": "E3", "fr": "F4" } { "en": "E4", "fr": "F1" } { "en": "E4", "fr": "F2" } { "en": "E4", "fr": "F3" } { "en": "E4", "fr": "F4" }

How can I get it to pair the first elements of each array, the second elements, etc.

Are .en and .fr always fixed? or keys name could be dynamic? — Inian
– Inian, Commented Oct 5, 2020 at 14:45
@Inian keys will change but I don't mind having a jq filter which is 'hardcoded' — jfrank
– jfrank, Commented Oct 6, 2020 at 15:33

peak · Accepted Answer · 2020-10-05 14:44:53Z

6

You could also use transpose to "zip" the arrays together:

[[.en,.fr] | transpose[] | {en:.[0], fr:.[1]} ]

answered Oct 5, 2020 at 14:44

peak

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1 Comment

jfrank Over a year ago

Nice ... thanks @peak, hadn't come across transpose before - does the job

choroba · Accepted Answer · 2020-10-05 14:30:06Z

I used range() to iterate over the elements of the arrays:

jq '[range(.en|length) as $i | {en: .en[$i], fr: .fr[$i]}]' file.json

peak · Accepted Answer · 2020-10-07 07:07:54Z

Here's a solution that will work with arbitrarily many keys and that does not require knowledge of the key names beforehand:

def objectify($keys): [$keys, .] | transpose | map({(.[0]): .[1]}) | add; keys_unsorted as $keys | [[.[]] | transpose[] | objectify($keys)]

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