equalTo()
🧭 API map
| I want to… | Details |
|---|---|
| See every accepted call style | Signatures |
| See common and advanced usage | Usage and behavior |
| Customize messages | Message configuration |
| Understand reactive constraints | Reactive behavior |
| Return to the complete catalog | Built-in validators |
📐 Signatures
equalTo(expectedValue)
equalTo(expectedValue, message)
equalTo(expectedValue, options)
Reactive constraint arguments use a zero-argument function. The function may read signals and,
where supported, return undefined to disable the constraint temporarily.
When declared inside a primitive call, this helper can use the consuming node's value type. A literal constraint may cover only part of a field's union without narrowing the field itself. Standalone declarations continue to infer their value type from the supplied constraint.
📖 Usage and behavior
Requires a value to equal a static or reactive expected value using Object.is():
const password = field('');
const myForm = form({
termsAccepted: field(false, [equalTo(true)]),
password,
confirmation: field('', [equalTo(() => password())]),
confirmedTerms: field(false, [
equalTo(true, 'You must accept the terms.'),
]),
});
Unlike optional format validators, null and undefined are compared as real values rather than skipped. Signals read by the expected-value source are tracked. A failure is { kind: 'equalTo', message }; both compared values are deliberately omitted so confirmation errors do not expose secrets.
💬 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 requireConfirmation = signal(false);
const password = signal('secret');
const confirmation = field('', [
equalTo(() => password(), { when: () => requireConfirmation() })
]);
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.