Number

Per-instance numeric holder: stores one number locally, optionally latching new values until a Set signal fires.

Number holds a single numeric value that belongs to this node instance alone — it is not named or shared (for an app-wide named value use Variable2). The value input sets it and savedValue (Value) reads it back. While the saveValue (Set) signal input is unconnected, values written to value apply immediately; once saveValue is connected the node latches: incoming values are held pending and only applied when Set fires. Incoming values are cast with JavaScript Number(), so non-numeric strings become NaN. changed fires only when the stored value actually changes; stored fires after every Set trigger.

When to use it

Use it to hold a local number — a counter, an index, a captured measurement — especially with the latch: feed a computed value into value and commit it with Set at the moment of an action. For simple increment/decrement a Counter is less wiring; for app-wide numbers use Variable2 + Set Variable.

At a glance


Category	Variables
Type name	`Number`
Available in	browser, cloud
SSR compatibility	safe
Provided by	`noodl-runtime`
Behaviour spec	version 2 (under the hood)

Inputs

Values

Name	Type	Default	Description
`runOnChange-value`	Boolean	`true`	Whether a new value on Value re-runs this node. On by default; untick to make this input passive so only the control signal runs it
`treatEmptyAs`	Enum (`null`, `zero`)	`null`	Back-compat for graphs written before Variables were nullable. `null` (default) keeps a cleared value distinguishable from a real 0. Choosing another option restores the pre-NDA-003 coercion for authors who relied on it.
`treatUnchangedAs`	Enum (`unchanged`, `done`)	`unchanged`	What this node reports when the action was valid and there was nothing to do. Unchanged (the default) keeps it a third outcome of its own. Done suits a project whose chains should carry on either way. Completed fires whatever this is set to.
`value`	Number	`0`	The empty-value contract (dev-docs/reference/EMPTY-VALUE-CONTRACT.md): `undefined` abstains and leaves the Variable's stored value untouched. `null` is a real value — it clears the Variable, is stored, and fires Changed. What "cleared" is stored as is controlled by `Treat empty as` (null by default).

Signals

Name	Type	Default	Description
`saveValue`	Signal	—	Stores the latest value now. This is additional to Value storing on change; untick Value under Run On Value Change to stop that

What each input does

Value (value)

undefined: ignored → Changed stays silent
the same as the last one, or Run On Value Change unticked: held for the next Set → Changed stays silent
a new value that converts to what is already stored: held, nothing changes → Changed stays silent
a new value, with Run On Value Change ticked: stored straight away (an empty one as Treat Empty As says) → Changed

Set (saveValue)

always: at the end of the frame the last Value is stored — Changed and Done if that changed it, otherwise Unchanged (or what Treat Unchanged As says)

Outputs

Values

Name	Type	Default	Description
`savedValue`	Number	—	Can be `null` — a cleared Variable (see `value`'s description) stores and emits null by default, not this type's zero value, unless `Treat empty as` says otherwise.

Signals

Name	Type	Default	Description
`changed`	Signal	—	Fires whenever the stored value actually changed, however it was reached — including Value writing straight through under Run On Value Change. It is a value-level event, not the outcome of a Set
`completed`	Signal	—	Fires after every invocation, whatever the outcome — wire this to carry on regardless. Failure still fires and still carries its reason, so this cannot hide an error
`done`	Signal	—	Fires when a Set stored a value the Variable was not already holding
`unchanged`	Signal	—	Fires when a Set stored the value it already held, so nothing changed. ⚠️ With Value left ticked under Run On Value Change this is the common case, because Value has already stored by the time Set fires

Patterns

Counter loop: savedValue → an Expression (count + 1) → value, with a click signal on saveValue — each click commits the incremented value. The latch prevents an infinite feedback loop.
savedValue → a Text's text: numbers cast to strings on delivery, so the count renders directly.

Watch out for

Wiring savedValue through an Expression back into value without connecting saveValue — with no latch the loop applies immediately and the value is unstable. Connect Set and drive it from a signal.

Examples

Click counter with a latched Number and a Boolean flag

The canonical per-instance counter: a Number node's savedValue feeds an Expression (count + 1) whose result loops back into the Number's value input. Because saveValue (Set) is connected, the incremented value is only committed when the Button's onClick fires — the latch is what makes the feedback loop safe. The count renders directly in a Text (number casts to string on delivery). A Boolean node shows the latch-a-signal-into-a-level shape: its value is pinned to true in parameters, the same click fires its Set, and its savedValue permanently reveals the hint text — a level, unlike the momentary click signal.

Counter, Expression, Number Remapper, Boolean, String, Variable

Code export

Exports to React. A project that uses it exports this node as React code.

How export works shows what an export writes, with a worked example.

Under the hood

This node's behaviour is written down as an executable spec in @nodegx/node-spec, version 2. The spec is the reference the conformance tests grade the runtime against. Every rule in it cites the line of the runtime it was read from. The full spec is at the bottom of this page.

What it depends on outside the node

Nothing. Its outputs depend only on its inputs and its own state.

Starting state

{
  "current": 0,
  "hasBeenSet": false,
  "sets": 0
}

How inputs are converted

Inputs not listed arrive as sent.

Input	Conversion	What it does
Value (`runOnChange-value`)	`not-false`	only an explicit `false` turns it off; no value, `0` and `""` leave it on

How actions report back

Each time Set is triggered, the node reports exactly one of Done or Unchanged.

The code it replaces

What you would write by hand instead:

a number held in state, set from elsewhere: const [price, setPrice] = useState(0)

The full spec

The spec's source, as the docs were generated. Helpers it imports live beside it in packages/nodegx-node-spec/src.

packages/nodegx-node-spec/src/nodes/number.ts
/**
 * Number — read from `packages/noodl-runtime/src/nodes/std-library/variables/number.ts` on
 * 2026-09-30 (NSP-011). The family's rules are in variable-base.ts; this file is the four lines
 * number.ts supplies.
 */

import { defineNode } from '../spec';
import { afterSets, CHANGED, onSet, onValue, SAVED_VALUE_DESCRIPTION, VARIABLE_OUTCOMES, variableInputs, variableState, type VariableArgs } from './variable-base';

/** :7-30 — startValue 0 (:10); `cast` is `Number(value)` (:22-24), NaN handled by the base (:17-21); empty options null / 0 (:25-28) */
export const NUMBER: VariableArgs & { type: 'number' } = {
  type: 'number',
  startValue: 0,
  cast: (value) => Number(value),
  emptyOptions: [
    { value: 'null', label: 'Null (default)', coerce: null },
    { value: 'zero', label: 'Zero (0)', coerce: 0 }
  ]
};

export const NumberVariable = defineNode({
  type: 'Number',
  // v2 (P109 ISL-027, row C5 ruled "Start with no remembered value"): a first Value of 0 is stored and fires
  // Changed like any other value, and a Set before any Value reports Unchanged. v1 ignored a first 0 (it equalled
  // a hidden seed of 0) and a Set before any Value stored that seed and reported Done.
  version: 2,
  source: 'packages/noodl-runtime/src/nodes/std-library/variables/number.ts',
  // NSP-018 — the hand-written code this node replaces (read by nothing yet; `spec-ledger` counts it)
  idioms: [
    { says: 'a number held in state, set from elsewhere', example: 'const [price, setPrice] = useState(0)' }
  ],
  state: variableState(NUMBER),
  inspect: (s) => String(s.current),
  outcomes: VARIABLE_OUTCOMES,
  inputs: variableInputs(NUMBER),
  outputs: {
    savedValue: { type: 'number', from: (s) => s.current, displayName: 'Value', group: 'Values', description: SAVED_VALUE_DESCRIPTION },
    changed: CHANGED
  }
}).on(
  { value: (s, v, i) => onValue(NUMBER, s, v, i), saveValue: onSet },
  { afterInputs: (s, i) => afterSets(NUMBER, s, i) }
);

Generated

This page is generated from node-catalog-enriched.json, the node's spec in packages/nodegx-node-spec and the export ledger. Do not edit it by hand — run npm run docs:nodes to regenerate, and fix the source instead.

When to use it​

At a glance​

Inputs​

Values​

Signals​

What each input does​

Outputs​

Values​

Signals​

Patterns​

Watch out for​

Examples​

Related nodes​

Code export​

Under the hood​

What it depends on outside the node​

Starting state​

How inputs are converted​

How actions report back​

The code it replaces​

The full spec​

When to use it

At a glance

Inputs

Values

Signals

What each input does

Outputs

Values

Signals

Patterns

Watch out for

Examples

Related nodes

Code export

Under the hood

What it depends on outside the node

Starting state

How inputs are converted

How actions report back

The code it replaces

The full spec