How can I specify the correct TypeScript type for the onClick event in a React Konva component?

General Discussions
1

How can I specify the correct TypeScript type for the onClick event in a React Konva component?

I am encountering a TypeScript error with event: any, and the property index on event.target is causing issues. How can I properly typescript onclick event to resolve this?

Here is my current approach:

interface KonvaTextEventTarget extends EventTarget {
  index: number;
}

interface KonvaMouseEvent extends React.MouseEvent<HTMLElement> {
  target: KonvaTextEventTarget;
}

// ...

return (
    key={index}
    x={position[0]}
    y={position[1]}
    fontSize={units}
    width={units}
    text={mark}
    fill={fill}
    fontFamily={'Helvetica'}
    align={'center'}
    onClick={(event: KonvaMouseEvent) => {
      makeMove(ownMark, event.target.index);
    }}
  
);
2

Hi,

One solution is to use Declaration Merging to define custom interfaces for the event target. Here’s how you can do it:

interface KonvaTextEventTarget extends EventTarget {
  index: number;
}

interface KonvaMouseEvent extends React.MouseEvent<HTMLElement> {
  target: KonvaTextEventTarget;
}
Then, you can use KonvaMouseEvent as the type for your onClick event:

onClick={(event: KonvaMouseEvent) => {
  makeMove(ownMark, event.target.index);
}}

While this approach resolves the TypeScript error and ensures type safety, it might feel a bit cumbersome. It’s useful for getting past type issues but could be seen as overly verbose.

3

You can handle this by typing the onClick event as React.MouseEventHandler and then using type assertion to access the specific properties.

Here’s how you can do it:

onClick: React.MouseEventHandler<HTMLElement> = (e) => {
  const target = e.target as HTMLDivElement; // Adjust the type according to your actual HTML element
  // Access the properties of the target here
}

This approach ensures type safety while accessing properties specific to your HTML elements. Adjust the type in the as clause according to the element you are working with.

4

You can use the correct type for the event as follows:

onClick: React.MouseEvent<HTMLButtonElement, MouseEvent> = (event) => {
  const target = event.target as HTMLButtonElement;
  // Access properties specific to HTMLButtonElement here
}

This specifies the event as a React.MouseEvent with HTMLButtonElement and MouseEvent, ensuring type safety for button elements.