Script functions

Reading the form

Function	Gives you
`value('key')`	The answer in another field. You can also write `key()` — every field is callable by its own key.
`parent('key')`	An answer on the enclosing record. Only inside a repeatable section or a subform entry; anywhere else it raises an error.
`rows('section')`	A repeatable section’s rows, as an array of objects. Empty array if none.
`user()`	Who is filling the form in: `{ id, name, email }`.
`isBlank(v)`	True for `null`, `undefined`, whitespace-only text and empty arrays.

Arithmetic

Function	Does
`SUM(...)`	Adds everything given. Non-numbers are ignored.
`AVG(...)`	Mean. `0` when there is nothing to average.
`MIN(...)`, `MAX(...)`	Smallest and largest. `null` when given nothing.
`COUNT(...)`	How many values are filled in. Flattens arrays; skips `null`, `undefined` and empty text.
`ROUND(n, places)`	Rounds. `places` defaults to 0. `null` if `n` is not a finite number.
`Math`	`PI`, `E`, `abs`, `ceil`, `floor`, `round`, `sqrt`, `pow`, `min`, `max`.

Dates, conversion and objects

Function	Gives you
`TODAY()`	Today as `YYYY-MM-DD`.
`NOW()`	The current moment as an ISO 8601 string.
`Number(v)`, `String(v)`, `Boolean(v)`	Conversion. `String(null)` gives `''`.
`parseInt(v, radix)`, `parseFloat(v)`, `isNaN(v)`	As expected. `radix` defaults to 10.
`Object.keys(o)`, `Object.values(o)`	For walking a repeatable row. `[]` for anything not an object.

The language

Ordinary JavaScript expressions and statements: const and let, if, for, for…of, while, arrow functions, template literals, optional chaining, ??. Not available: anything that reaches outside the form — fetch, window, document, localStorage, import.

A field whose key collides with a function name — a field called sum, say — does not get the sum() shorthand. The function wins, and you read that field with value('sum').

What each kind of script should return

Kind	Return
Value	the value to write into the field
Condition	truthy to show the field, falsy to hide it
Validation	`true` if acceptable; a string to reject with that message; `false` to reject with a generic one