React Hooks Form : undefined values on submit

Question

I took the example from the documentation :

import React from "react";
import { useForm } from "react-hook-form";

export default function App() {
  const { register, handleSubmit, watch, formState: { errors } } = useForm();
  const onSubmit = data => console.log(data);

  console.log(watch("example")); 

  return (
    <form onSubmit={handleSubmit(onSubmit)}>
      <input defaultValue="test" {...register("example")} />
      <input type="submit" />
    </form>
  );
}

But on every change or on submit, I got undefined for each field

I tried to install the library again but nothing change and I got undefined everywhere...seems to be a problem with the register function. Does anybody got the same issue ?

Answer 1

With v7 the usage of register changed as noted in the comments. If you still need to use v6, you have to write it like this:

function App() {
  const { register, handleSubmit, watch, formState: { errors } } = useForm();
  const onSubmit = data => console.log(data);

  console.log(watch("example")); 

  return (
    <form onSubmit={handleSubmit(onSubmit)}>
      <input defaultValue="test" name="example" ref={register} />
      <input type="submit" />
    </form>
  );
}

Docs v6

Answer 2

In my case it was a typo:

<input defaultValue="test" {...(register('name'), { required: true })} />

// submit => { name: undefined }

Instead of:

<input defaultValue="test" {...(register('name', { required: true }))} />

// submit => { name: "test" }

Hopefully it can help someone else.

Answer 3

In my case, I was using a Controller, so to fix the Undefined value I just had to pass defaultValues to useForm. See the rules section here: https://react-hook-form.com/api/useform/watch

 const { register, handleSubmit, control, setValue} = useForm<MyFormValues>({
    defaultValues : {
      receiveUpdates: false
    }
  });

<Controller
  control={control}
  name="receiveUpdates"
  render={({ field }) => (
    <FormControlLabel
      control={
        <Checkbox
          ref={field.ref}
          checked={field.value}
          onChange={field.onChange}
        />
      }
      label="Receive Email Updates?"
      labelPlacement="start"
    />
  )}
/>