Create a new json string from jq output elements - json

Question

My jq command returns objects in brackets but without comma separators. But I would like to create a new json string from it.
This call finds all elements of arr that have a FooItem in them and then returns texts from the nested array at index 3:
jq '.arr[] | select(index("FooItem")) | .[3].texts'
on this json (The original has more elements ):
{
"arr": [
[
"create",
"w199",
"FooItem",
{
"index": 0,
"texts": [
"aBarfoo",
"avalue"
]
}
],
[
"create",
"w200",
"NoItem",
{
"index": 1,
"val": 5,
"hearts": 5
}
],
[
"create",
"w200",
"FooItem",
{
"index": 1,
"texts": [
"mybarfoo",
"bValue"
]
}
]
]
}
returns this output:
[
"aBarfoo",
"avalue"
]
[
"mybarfoo",
"bValue"
]
But I'd like to create a new json from these objects that looks like this:
{
"arr": [
[
"aBarfoo",
"avalue"
],
[
"mybarfoo",
"bValue"
]
]
}
Can jq do this?
EDIT
One more addition: Considering that texts also has strings of zero length, how would you delete those/not have them in the result?
"texts": ["",
"mybarfoo",
"bValue",
""
]

Answer 1

You can always embed a stream of (zero or more) JSON entities within some other JSON structure by decorating the stream, that is, in the present case, by wrapping the STREAM as follows:
{ arr: [ STREAM ] }
In the present case, however, we can also take the view that we are simply editing the original document, and accordingly use a variation of the map(select(...)) idiom:
.arr |= map( select(index("FooItem")) | .[3].texts)
This latter approach ensures that the context of the "arr" key is preserved.
Addendum
To filter out the empty strings, simply add another map(select(...)):
.arr |= map( select(index("FooItem"))
| .[3].texts | map(select(length>0)))