json - How to check if element exists in array with jq

Question

I have an array and I need to check if elements exists in that array or to get that element from the array using jq, fruit.json:

{
    "fruit": [
        "apple", 
        "orange",
        "pomegranate",
        "apricot",
        "mango"
    ]
}


cat fruit.json | jq '.fruit .apple' 

does not work

Answer 1

The semantics of 'contains' is not straightforward at all. In general, it would be better to use 'index' to test if an array has a specific value, e.g.

.fruit | index( "orange" )

However, if the item of interest is itself an array, the general form:

 ARRAY | index( [ITEM] )

should be used, e.g.:

[1, [2], 3] | index( [[2]] )  #=> 1

IN/1

If your jq has IN/1 then a better solution is to use it:

.fruit as $f | "orange" | IN($f[])

If your jq has first/1 (as does jq 1.5), then here is a fast definition of IN/1 to use:

def IN(s): first((s == .) // empty) // false;

any(_;_)

Another efficient alternative that is sometimes more convenient is to use any/2, e.g.

any(.fruit[]; . == "orange")

or equivalently:

any(.fruit[] == "orange"; .)