Why 'input' event has `Event` type of event instead of `InputEvent`

[kaczor6418]

TypeScript/lib/lib.dom.d.ts

Line 5715 in da5ff57

"input": Event;

Hi I am wondering why type of 'input' event type is a Event type (I thought it should be InputEvent)?

I came across on this problem doing this:

interface OnInputTextFieldListenerProps extends BaseTextFieldListenerProps {
    eventName: Extract<keyof GlobalEventHandlersEventMap, 'input'>;
    callback(e?: InputEvent): void;
}

if (isOnInputTextFieldProps(listenerProps)) {
    this.input.addEventListener<'input'>(listenerProps.eventName, listenerProps.callback.bind(this));
}

And now I am getting this error:

TS2345: Argument of type '(e?: InputEvent | undefined) => void' is not assignable to parameter of type '(this: HTMLInputElement, ev: Event) => any'.

Which is absolutely correct.

But why GlobalEventHandlersEventMap 'input' is typed as Event instead of InputEvent. If MDN documentation says that GlobalEventHandlers.oninput interface is InputEvent. oninput is probalby equivalent of typescript input. I think like that because in MDN docs every key of GlobalEventHandlers interface starts with on.

You can find this GlobalEventHandlersEventMap interface here lib.dom.d.ts - L:5715 at line 5715.

I also created a question at StackOverflow - Why 'input' event has Event type of event instead of InputEvent

[andrewbranch]

I believe the answer to this is that InputEvent is, as MDN says, an “experimental technology” covered in a draft specification, and not in the HTML living standard, which says the event interface is Event. MDN’s browser compatibility table indicates only partial support, which means, depending on where your code runs, you may or may not in fact have an InputEvent, but you’ll definitely have an Event. I’m not sure what our threshold of usage/support is for changing our DOM typings—maybe @sandersn can comment.

To be both run-safe and type-safe, your callback parameter should take an event, and then check e instanceof InputEvent (or even typeof InputEvent !== "undefined" && e instanceof InputEvent if you want to be extra careful with super old browsers) before accessing InputEvent-specific properties. (Even there, you should be careful, since some browsers may support InputEvent but not every property that the draft spec says exists.)

[kaczor6418]

@andrewbranch thank you for your answer

[wbt]

Is browser support strong enough now to change it? We are already using InputEvent on 'beforeinput' and it would be helpful to have it on 'input' too.

[andrewbranch]

It looks like there’s another issue: microsoft/TypeScript-DOM-lib-generator#1174