jq: How to replace element in an array or add it if it doesn't exist

Question

Given the following json structure:

{
   "elements": [
      {
         "name": "disregard",
         "value": "me"
      },
      {
         "name": "foo",
         "value": "bar"
      },
      {
         "name": "dont-edit",
         "value": "me"
      }
   ]
}

What would be the appropriate jq query to replace the value of the name: foo element or create/add the element to the array, if it doesn't already exist?

I removed the elipsis, so it's valid JSON. I hope that's what you meant by mre @oguzismail. If you meant an actual query, well then I wouldn't be asking this question, if I could provide that. :) — carlossless
– carlossless, Commented Oct 4, 2019 at 16:07
@carlossless, I have edited your input so that it's a valid JSON — Dmitry
– Dmitry, Commented Oct 4, 2019 at 19:12
Carlossness - You're supposed also to show some attempt at a solution (even if it's not in jq). @Dmitry - It's still not valid JSON! — peak
– peak, Commented Oct 4, 2019 at 19:39
@peak, yes, it is, however, you probably don't see it yet, due to awaiting a peer review — Dmitry
– Dmitry, Commented Oct 4, 2019 at 19:42

peak · Accepted Answer · 2019-10-04 20:53:42Z

8

Here is a safe if pedestrian solution:

.elements 
|=  (map(.name) | index("foo")) as $ix
    | if $ix 
      then .[$ix]["value"] = "BAR" 
      else . + [{name: "foo", value: "BAR"}]
      end

You might want to abstract away the "foo" and "BAR" bits:

upsert

# Input is assumed to be an array of {name:_, value:_} objects
def upsert($foo; $bar):
  (map(.name) | index($foo)) as $ix
  | if $ix then .[$ix]["value"] = $bar else . + [{name: $foo, value: $bar}] end;

Usage:

.elements |= upsert("foo"; "BAR")

edited Oct 4, 2019 at 20:53

answered Oct 4, 2019 at 19:57

peak

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2 Comments

Hooch Over a year ago

This is what I'm looking for. But how to deal with issue if .elements doesn't exists? I would need to create that .elements node if id doesn't exists and add entry to it.

peak Over a year ago

If you also want to cover the case that there is no key named "elements" in the object, then use the form .element |= if . == null then ..... else AS_BEFORE end

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