Create a custom synchronous validator for an Angular Reactive Form
Tests your grasp of the ValidatorFn contract and reactive form wiring. A strong answer: a function accepting AbstractControl returns null when valid or an error object when invalid, passed as the second FormControl argument. Red flag: returning booleans.
Tests your grasp of the ValidatorFn interface and reactive form wiring. A good answer hits four things in order: first, write a plain function that accepts an AbstractControl and reads its value; second, return null for valid or a ValidationErrors object for invalid; third, pass it as the second argument to the FormControl constructor or via setValidators; fourth, read errors with control.hasError or control.errors.
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- #reactive forms
- #validators
- #frontend
- #typescript
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