Merge Arbitrary Amount of Arrays into Single Array? - arrays

Question

I have a series of JSON files that I've been working with via jq. Each file consists of an array of dictionaries, e.g.
file1.json: [{ "id": 1 }]
file2.json: [{ "id": 2 }]
The only command I have found which successfully merges all input files into one output array is:
jq --slurp '.[0] + .[1]' file1.json file2.json
This command outputs [{ "id": 1 }, { "id": 2 }], as expected.
I'm writing a shell script which is expected to merge a variable set of files into a single JSON array as an output. My script will execute something like:
find . -type f -iname '*.json' | xargs jq 'FILTER'
This should invoke jq like jq 'FILTER' file1.json file2.json ....
Is there a feature that I'm missing that will take all input files and first merge them into one contiguous list of objects without having to rewrite the filter to something like .[0] + .[1] + .[2] ...?

Answer 1

Given:
1.json
[{ "id": 1 }]
2.json
[{ "id": 2 }]
3.json
[{ "id": 3 }]
Then this command:
jq --slurp 'map(.[])' 1.json 2.json 3.json
Returns:
[
{
"id": 1
},
{
"id": 2
},
{
"id": 3
}
]
Or simply:
jq --slurp 'flatten' 1.json 2.json 3.json

Answer 2

It's generally best to avoid the -s option, especially if your version of jq supports inputs, as do all versions >= 1.5.
In any case, if your version of jq supports inputs, you could write:
jq -n '[inputs[]]' 1.json 2.json 3.json # etc
or whichever variant meets your needs.
Otherwise, you could simply write:
jq -s add 1.json 2.json 3.json # etc
Note on flatten
flatten itself is ruthless:
$ jq flatten <<< '[[[1], [[[[2]]]]]]'
[1,2]
flatten(1) is less so.