groupBy

The groupBy function groups the elements of an array by a derived key expression, producing a map where each key maps to an array of matching elements.

Syntax

<array>.groupBy(expr)

Arguments

• expr - An expression evaluated against each element to determine its group key. The result must be a string, int, float, or bool. Use $this to refer to the current element and $key to refer to the current index.

Examples

Group primitives

[1, 2, 3, 1, 2].groupBy($this)
// {"1": [1, 1], "2": [2, 2], "3": [3]}

Group objects by a field

[
    {"name": "Alice", "dept": "eng"},
    {"name": "Bob", "dept": "eng"},
    {"name": "Carol", "dept": "sales"}
].groupBy(dept)
// {"eng": [{"name": "Alice", "dept": "eng"}, {"name": "Bob", "dept": "eng"}], "sales": [{"name": "Carol", "dept": "sales"}]}

Group by a boolean expression

[3, 7, 1, 8, 5].groupBy($this > 5)
// {"false": [3, 1, 5], "true": [7, 8]}

CLI usage

$ cat users.json | dasel 'groupBy(role)'

Chained with other functions

[
    {"name": "Alice", "dept": "eng"},
    {"name": "Bob", "dept": "eng"},
    {"name": "Carol", "dept": "sales"}
].groupBy(dept).eng
// [{"name": "Alice", "dept": "eng"}, {"name": "Bob", "dept": "eng"}]