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between()

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📐 Signatures​

between(minimum, maximum)
between(minimum, maximum, message)
between(minimum, maximum, options)

Reactive constraint arguments use a zero-argument function. The function may read signals and, where supported, return undefined to disable the constraint temporarily.

📖 Usage and behavior​

Requires a number within an inclusive range:

const myForm = form({
  age: field(17, [between(18, 65)]),
  dependentAge: field(70, [
    between(
      () => allowedAge().minimum,
      () => allowedAge().maximum,
    ),
  ]),
  employeeAge: field(70, [
    between(18, 65, 'Enter an age within the supported range.'),
  ]),
});

null and NaN pass. If either boundary resolves to undefined or NaN, the complete range is temporarily disabled. A failure is { kind: 'between', min, max, actual, message }. Both boundaries contribute to min() and max() metadata.

💬 Message configuration​

Every failure has a default English message. Where supported, pass a string as the final argument or use an options object for a static or reactive message, as shown above.

A message function may read signals. Returning undefined continues through node, Angular provider, process-wide, and built-in message fallbacks. See Validator messages.

⚡ Reactive behavior​

The options object accepts a reactive when predicate. Signals read from its validator context are tracked; while it returns false, the rule contributes neither errors nor constraint metadata.

const validateRange = signal(false);
const guests = field(12, [
  between(1, 10, { when: () => validateRange() })
]);

Reactive constraint functions and message functions track the signals they read. When a resolved constraint becomes unavailable, validators that support optional constraint sources temporarily stop contributing their error and metadata.

The validator runs synchronously as part of its node's validator source. Disabled, readonly, and hidden nodes skip validation until they become interactive again.

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