Question 1

Template-driven vs reactive forms in Angular?

Accepted Answer

Template-driven uses ngModel in templates; reactive builds FormControl/FormGroup in the class. Reactive forms scale better for complex validation and dynamic controls. Template-driven is fine for simple forms. Prefer reactive for enterprise apps.

Question 2

How do FormControl, FormGroup, and FormArray relate?

Accepted Answer

Controls are leaves; groups nest controls; arrays hold variable-length control lists. Compose nested structures for complex models. value/statusChanges observe updates. disable() excludes from values by default.

Question 3

How do you create a custom validator?

Accepted Answer

Return a function (AbstractControl) => ValidationErrors | null; async validators return Observable/Promise. Register on controls via validators array. Cross-field validators belong on the group. Keep validators pure.

Question 4

How do you show validation errors accessibly?

Accepted Answer

Bind error messages when control touched/dirty, use aria-describedby, and set aria-invalid. Don't show errors before interaction unless after submit. Focus first invalid control on submit.

Question 5

What is the difference between value and getRawValue()?

Accepted Answer

value omits disabled controls; getRawValue includes them. Important when disabling fields for UX but still needing their data on submit.

Question 6

Design a dynamic form where fields come from a JSON schema.

Accepted Answer

Build FormGroup/FormArray from schema at runtime; render controls with @for; attach validators from metadata. Centralize schema→control mapping. Consider performance for large schemas. Validate server-side too.

Forms Angular Interview Questions

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