How do EventEmitter<undefined> and EventEmitter<void> differ from each other?

Question

How do EventEmitter<undefined> and EventEmitter<void> differ from each other?

At times, there may be a situation where we need to omit the generic variable. For example:

@Component( ... )
class MyComponent {

  @Output()
  public cancel = new EventEmitter<undefined>();

  private myFoo() {
    this.cancel.emit(); // no value needs to be passed
  }
}

Now, here comes the question: What is the better way to define the EventEmitter type?
EventEmitter<undefined> or EventEmitter<void>.

void is preferable because no argument is required in the .emit() method call.
undefined is better as .emit() functions similarly to .emit(undefined).

What are your thoughts on this matter?

angular typescript

Answer 1

Answer №1

As stated in the TypeScript documentation, the void type allows for both undefined and null values. This means that the provided code snippet would be considered valid:

@Component( ... )
class MyComponent {

  @Output()
  public cancel = new EventEmitter<void>();

  private myFoo() {
    this.cancel.emit();
    this.cancel.emit(undefined);
    this.cancel.emit(null);
  }
}

In contrast, if using EventEmitter<undefined>, you are limited to passing only undefined or no argument at all. While it may be more accurate in your specific case, there shouldn't be any major issues if you choose to pass null to an emitter where a value is not anticipated. Therefore, opting for void might be preferable due to its brevity.

Answer 2

As stated in the TypeScript documentation, the void type allows for both undefined and null values. This means that the provided code snippet would be considered valid:

@Component( ... )
class MyComponent {

  @Output()
  public cancel = new EventEmitter<void>();

  private myFoo() {
    this.cancel.emit();
    this.cancel.emit(undefined);
    this.cancel.emit(null);
  }
}

In contrast, if using EventEmitter<undefined>, you are limited to passing only undefined or no argument at all. While it may be more accurate in your specific case, there shouldn't be any major issues if you choose to pass null to an emitter where a value is not anticipated. Therefore, opting for void might be preferable due to its brevity.

How do EventEmitter<undefined> and EventEmitter<void> differ from each other?

Answer №1

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