How can you sort a JSON object efficiently using JQ

Question

I've got JSON in the format

{
  "a": {
    "size":3
  },
  "b": {
    "size":2
  },
  "c": {
    "size":1
  }
}

I need to sort it by size, e.g.:

{
  "c": {
    "size": 1
  },
  "b": {
    "size": 2
  },
  "a": {
    "size": 3
  }
}

I have found a way to do it, e.g.:

. as $in | keys_unsorted | map ({"key": ., "size" : $in[.].size}) | sort_by(.size) | map(.key | {(.) : $in[.]}) | add

but this seems quite complex so I'm hoping there's a simpler way that I've overlooked?

Answer 1

You can use to_entries / from_entries, like this:

jq 'to_entries|sort_by(.value.size)|from_entries' file.json

to_entries will transform your input object into a list of key/value pair objects:

[
  {
    "key": "a",
    "value": {
      "size": 3
    }
  },
  ...
  {
    "key": "c",
    "value": {
      "size": 1
    }
  }
]

That allows to apply sort_by(.value.size) to that list and then convert it back to an object using from_entries.