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lesserThan

Validate that a numeric value is strictly less than another field's numeric value.

Signature​

NguardValidators.Number.lesserThan(fieldKey: string): ValidatorFn
ParameterTypeDescription
fieldKeystringThe key of the sibling field to compare against

Reactive forms​

import { FormControl, FormGroup } from '@angular/forms';
import { NguardValidators } from 'ng-nguard';

const range = new FormGroup({
    ceiling: new FormControl(0),
    floor: new FormControl(0, [
        NguardValidators.Number.lesserThan('ceiling'),
    ]),
});

Template-driven forms​

<input ngModel name="ceiling" type="number" />
<input ngModel name="floor" type="number" [nguardLesserThan]="'ceiling'" />

Error key​

{ lesserThan: true }

Notes​

  • The check is strict (<). Equal values fail.
  • Both fields must be numeric — non-numeric inputs (including a non-numeric sibling) cause failure.
  • If the control has no parent form group, the validator fails.
  • Numeric strings are accepted on both sides.

See also​