I'm trying to get the correct type for this function parameter

  const handleInputChange = ({ target }) => {
    setFormValues({
      ...formValues,
      [target.name]: target.value,
    });
  };

<iframe name="sif1" sandbox="allow-forms allow-modals allow-scripts" frameborder="0"></iframe>

its throwing me an error that didn't crash the app but I know its not a good practice.

to give more context, all the fields that are changing are strings.

CodePudding user response：

It's telling you that because you haven't told it what the type of the parameter is.

You need to tell it what the type is. There are a couple of ways:

1. Type the constant you're assigning the function to; or

2. Directly type the parameter

Type the constant you're assigning the function to

You can do that with the ChangeEventHandler type, which is generic, taking the type of the element as a type argument:

import { ChangeEventHandler } from "react";

// ...

const onChange: ChangeEventHandler<HTMLInputElement> = ({currentTarget}) => {
// type −−−−−−^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    console.log(`${currentTarget.name} => ${currentTarget.value}`);
};

Directly type the parameter

The parameter is an event object which has a currentTarget property, so if (for instance) this is being used on an HTMLInputElement, you can use the type { currentTarget: HTMLInputElement }:

const handleInputChange = ({ currentTarget }: { currentTarget: HTMLInputElement }) => {
// type −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    // ...
};

Or you can use ChangeEvent<T>:

import { ChangeEvent } from "react";

// ...

const handleInputChange = ({ currentTarget }: ChangeEvent<HTMLInputElement>) => {
// type −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    // ...
};

---

Note I used currentTarget rather than target. It doesn't usually matter for input elements (target and currentTarget are always be the same if the handler is on the input, not its parent/ancestor), but it does for button elements and some others (since target might be a descendant element). And it matters if you're handling change on a parent/ancestor element instead of on the input directly.