Value map with JQ

Question

I've a large JSON file where I'd like to transform some values based on some kind of mapping.

The data I have looks like:

[
    {"id":1, "value":"yes"},
    {"id":2, "value":"no"},
    {"id":3, "value":"maybe"}
]

And I'd like to transform that into a list like this:

[
    {"id":1, "value":"10"},
    {"id":2, "value":"0"},
    {"id":3, "value":"5"}
]

With the fixed mapping:

yes => 10
no => 0
maybe => 5

My current solution is based on a simple if-elif-else combination like this:

cat data.json| jq '.data[] | .value = (if .value == "yes" then "10" elif .value == "maybe" then "5"  else "0" end)'

But this is really ugly and I'd love to have a more direct way to express the mapping.

Thanks for your help

Answer 1

If one wants to avoid having to specify the mapping on the command line, then the following two variants may be of interest.

The first variant can be used with jq 1.3, jq 1.4 and jq 1.5:

def mapping: {"yes":"10","no":"0","maybe":"5"};
map(.value |=  mapping[.])

The next variant uses the --argfile option (available since jq 1.4), and is of interest if the mapping object is available in a file:

jq --argfile mapping mapping.jq 'map(.value |= $mapping[.])' data.json

Finally, in jq 1.5, other alternatives based on import are also available (!).

Answer 2

Here is a solution which uses an "inline" object since the mapping is small:

map(.value = {"yes":"10","no":"0","maybe":"5"}[.value])

which can be shorted with |= as in peak's solution to:

map(.value |= {"yes":"10","no":"0","maybe":"5"}[.])