Arrays

• . : distribute a property access over array elements
• [bool] : keep elements matching a boolean predicate
• [number] : access an element by index
• ^(key) : sort elements by one or more keys
• count / sum / join : collapse an array to a scalar
• Playground

Typeflow has no loops — array work is done with four postfix constructs (distribution, [filter], [index], ^(sort)) plus projection and the aggregate functions.

Operator	Effect
.	distribute a property access over array elements
[bool]	keep elements matching a boolean predicate
[number]	access an element by index
^(key)	sort elements by one or more keys
count / sum / join	collapse an array to a scalar

. : distribute a property access over array elements

Accessing a property on an array of objects distributes over the elements — labels.name on { name: string }[] yields string[].

names: user.labels.name

[bool] : keep elements matching a boolean predicate

A boolean expression in brackets keeps matching elements. Inside the brackets you are in element scope: bare identifiers resolve on the element. The predicate must be boolean — user.labels[name] is rejected (TF2009).

active: user.labels[active]
activeNames: user.labels[active].name

[number] : access an element by index

Indexing yields element | undefined (the array may be shorter), so further access needs ?..

first: user.labels[0]
firstName: user.labels[0]?.name
firstOr: user.labels[0]?.name ?? "none"

^(key) : sort elements by one or more keys

Sorts a copy of the array by each key in turn. Keys are expressions in element scope; prefix a key with > for descending (< or nothing for ascending). A key must be a number or a string (TF2011); nullish keys sort last.

alphabetical: user.labels^(name).name
bestFirst: user.labels^(>score, name)

count / sum / join : collapse an array to a scalar

See Functions for the full aggregate list.

games: count(stats.scores)
total: sum(stats.scores)
tagLine: join(stats.tags, ", ")

Playground

Mapping✔Playground ↗

input stats: { scores: number[], tags: string[] }

map {
  games: count(stats.scores),
  total: sum(stats.scores),
  tagLine: join(stats.tags, ", "),
}

input stats: { scores: number[], tags: string[] } map { games: count(stats.scores), total: sum(stats.scores), tagLine: join(stats.tags, ", "), }

Input JSON

{ "scores": [10, 20, 12], "tags": ["math", "pioneer"] }

{ "scores": [10, 20, 12], "tags": ["math", "pioneer"] }

Output

{
  "games": 3,
  "total": 42,
  "tagLine": "math, pioneer"
}

inferred type{ games: number; total: number; tagLine: string }

Next: Projection.