Hello, I have a problem:
I writing an event handler for invalid input from a html form element in order to get a validation on real time:

FFormulario1            :=
TJSHTMLFormElement(document.getElementById('informacion1'));
FFormulario1.oninvalid  ;

before I defined

function Form2Validacion(aEvent: TJSEventhandler): Boolean;
begin
  window.alert('Hay un campo con valores incorrectos!!!');
end;

knowing in web.pas say:
TJSHTMLFormElement = class external name 'HTMLFormElement' (TJSHTMLElement)

 TJSHTMLElement = class external name 'HTMLELement' (TJSElement)
 public
 oninvalid : TJSEventhandler;
 ...

but Lazarus in compile time shut me:
project1.lpr(262,28) Error: Incompatible type arg no. 1: Got "TEventListenerEvent", expected "TJSEventHandler"

if I change to:
function Form2Validacion(aEvent: TEventListenerEvent): Boolean;

and then Lazarus compiles Ok!!!

but my browser claim to me with all justice:
TypeError: $mod.FFormulario1 is null!!!!

it will be an Error???

Thanks

pp

Exactly. I think it is a bug.

HTML DOM events allow JavaScript to register different event handlers on elements in an HTML document.
I think these events, for instance:

oninput :  TJSEventhandler;

should be declared to another type:

oninput :  TJSRawEventHandler;
procedure OnInput(aEvent: TJSEvent);
begin
  console.log(aEvent.target);
end;

I think the correct TJSEventHandler type definition is:

TJSEventHandler = reference to function(event: TJSEvent): Boolean;

TJSEventhandler is defined as
  TJSEventHandler = reference to function(Event: TEventListenerEvent): boolean;

Correct.

if I change to: function Form2Validacion(aEvent: TEventListenerEvent): Boolean; and then Lazarus compiles Ok!!!

Yes.

but my browser claim to me with all justice: TypeError: $mod.FFormulario1 is null!!!!

That probably means
document.getElementById('informacion1')
returned nil.

Check if FFormulario1 is nil and if "informacion1" is correct. Case sensitive.

Mattias

warleyalex wrote

I think the correct TJSEventHandler type definition is: TJSEventHandler = reference to function(event: TJSEvent): Boolean;

You are right.

And this is in fact the TJSRawEventHandler prototype (barring the boolean result). The reason was in the confusing documentation about javascript event handlers.

The best option is probably to redefine TEventListenerEvent = TJSEvent. That will make both eventhandler types identical, and should remain backwards compatible.

Michael.