JMESPath · lesson 11 of 15 · Reshaping

Multiselect hash

{key: expression, …} builds an object, so you can rename, pick and combine values.

Example 1Rename fields

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[*].{who: name, years: age}

{who: name, years: age} Build an object for each member: the key who gets the name and years gets the age.

Result

[
  {"who":"Ada","years":36},
  {"who":"Linus","years":28},
  {"who":"Grace","years":45},
  {"who":"Alan","years":41}
]

Try it in the playground

Example 2A summary object

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

{team: team, count: length(members), oldest: max_by(members, &age).name}

team: team Copy a value under a key.
count: length(members) A computed value.
oldest: max_by(members, &age).name Functions and paths combine freely.

Result

{"count":4,"oldest":"Grace","team":"Platform"}

Try it in the playground

Good to know

Objects come back with their keys in alphabetical order, not the order you wrote them.