jq · lesson 15 of 32 · Transforming

Working with objects

keys lists the key names, has(k) tests for one, a + b merges two objects (the right side wins), and with_entries(f) rewrites keys and values through {key, value} pairs.

Example 1Key names, and whether a key exists

Document

{
  "team": "Platform",
  "office": { "city": "Berlin", "floor": 3 },
  "members": [
    { "name": "Ada", "age": 36, "role": "lead", "active": true,
      "email": "[email protected]", "skills": ["rust", "sql"] },
    { "name": "Linus", "age": 28, "role": "dev", "active": true,
      "email": null, "skills": ["c", "shell"] },
    { "name": "Grace", "age": 45, "role": "dev", "active": false,
      "skills": ["cobol"] },
    { "name": "Alan", "age": 41, "role": "qa", "active": true,
      "email": "[email protected]", "skills": [] }
  ]
}

Query

.office | keys, has("city")

keys The object's key names, as a sorted array.
has("city") Does the key exist? → true.

Result

["city","floor"]
true

Try it in the playground

Example 2Merge, then rewrite every value

Document

{
  "team": "Platform",
  "office": { "city": "Berlin", "floor": 3 },
  "members": [
    { "name": "Ada", "age": 36, "role": "lead", "active": true,
      "email": "[email protected]", "skills": ["rust", "sql"] },
    { "name": "Linus", "age": 28, "role": "dev", "active": true,
      "email": null, "skills": ["c", "shell"] },
    { "name": "Grace", "age": 45, "role": "dev", "active": false,
      "skills": ["cobol"] },
    { "name": "Alan", "age": 41, "role": "qa", "active": true,
      "email": "[email protected]", "skills": [] }
  ]
}

Query

.office + {country: "DE"} | with_entries(.value |= tostring)

+ {country: "DE"} Merge two objects: country is added, and on a clash the right side wins.
with_entries( Turn the object into {key, value} pairs, run the filter on each pair, and rebuild an object.
.value |= tostring Update each pair's value to a string — so 3 becomes "3".

Result

{"city":"Berlin","floor":"3","country":"DE"}

Try it in the playground

Good to know

to_entries and from_entries are the two halves of with_entries: .office | to_entries gives [{"key":"city","value":"Berlin"}, …].

Working with objects

Examples

Example 1Key names, and whether a key exists

Document

Query

Result

Example 2Merge, then rewrite every value

Document

Query

Result

Good to know