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"; .)