jq · lesson 4 of 32 · Getting started

Iterate & collect

.[] turns an array into a stream of its elements — one output each. Wrap any filter in [ … ] to collect a stream back into a single array.

Example 1Stream every member's name

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

.members[].name

.members The array of members.
[] Iterate: emit each element as its own output instead of the array.
.name Read name from every element — four separate results.

Result

"Ada"
"Linus"
"Grace"
"Alan"

Try it in the playground

Example 2Collect a stream into one array

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

[.members[].age]

[ Square brackets around a filter collect everything it outputs…
.members[].age …here, every member's age…
] …into one array — a single result.

Result

[36,28,45,41]

Try it in the playground

Good to know

.[] also iterates over the values of an object: .office[] gives "Berlin" then 3.