JMESPath · lesson 13 of 15 · Functions

Sorting & picking

sort_by, min_by and max_by take an expression reference: &age means "evaluate age on each element" rather than evaluating it right now.

Example 1Sort by a field

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

sort_by(members, &age)[*].name

sort_by( Sort an array by a key…
members …this array…
&age …the key, as a reference: & postpones age so it is evaluated on every element.
[*].name Then project the names, youngest first.

Result

["Linus","Ada","Alan","Grace"]

Try it in the playground

Example 2The element with the largest 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

max_by(members, &age).name

max_by(members, &age) The member with the largest age — the whole object.
.name Read its name → "Grace".

Result

"Grace"

Try it in the playground

Good to know

sort(list) sorts plain values and reverse(list) flips a list: reverse(sort_by(members, &age))[*].name sorts oldest first.
min_by is the counterpart of max_by.