Getting the following error: Unhandled Runtime Error SyntaxError: Unexpected end of input

Question

I am trying to send info to the backend(node.js express server) from the frontend(next.js) with the react hook form lib.

const test = () =>{
    const { register, handleSubmit, watch, formState: { errors } } = useForm();
    const onSubmit = async data => {
        const result = await fetch('http://localhost:5000/test', {mode: 'no-cors'},{
            method: 'POST',
            body: JSON.stringify(data),
            headers: {'content-type': 'application/json'}
        }).then(res=>res.json())
        console.log(data);
    }
    return(
        <div>
            <form onSubmit={handleSubmit(onSubmit)}>
            <input {...register("example")} />
            <input type="submit" />
            </form>
        </div>
    );
}

export default test;

and this simple .post request on the backend:

app.get('/', (req, res)=>{
    res.send('test success');
})

the error is on the following line: }).then(res=>res.json())