Query syntax

Overview

Dasel queries are composed of one or more statements. Each statement describes how to navigate or transform the data, and the final statement determines the output value.

A statement is made up of a sequence of accessors or function calls, chained together with a dot (.) and terminated with a semi-colon (;).

• Accessors let you step into nested structures (e.g. objects, arrays, maps).

• Functions apply transformations or filters to the current value.

Example

Suppose you have the following JSON document:

{
  "users": [
    {
      "id": 1,
      "name": "Alice",
      "active": true
    },
    {
      "id": 2,
      "name": "Bob",
      "active": false
    }
  ]
}

A dasel query might look like this:

$activeUsers = $root.users.filter(active == true);
$activeUsers.map(name)

• $activeUsers = Variable assignment.

• $root Access the root document.

• users Access the users field.

• filter(active == true) Filter the users list to only include elements where active is true.

• ; Terminate the statement.

• $activeUsers Access the active users variable we just created.

• map Iterate through each active user, returning the specified value, in this case name . (Since this is the last statement, this is also the output value.)

Output:

[
  "Alice"
]

This query could be written in a more compact form, or split into multiple statements for clarity. The following examples are equivalent and will all produce the same result:

$root.users.filter(active == true).map(name)

$activeUsers = $root.users.filter(active == true);
$activeUsers.map(name)

$activeUsers = $root.users.filter(active == true);
$names = $activeUsers.map(name);
$names