How to pass an object to another page using the useRouter from 'next/navigation'?

I am on one page, and I want to redirect the user to another page.
I would like to send an object to the new page using the hook useRouter from next/navigation because I'm using the app directory. How can I change the code below to pass an object?

import { useRouter } from 'next/navigation'  
const router = useRouter()
router.push('/dashboard')

If I were using the page directory, I would do it like this:

import { useRouter } from 'next/router'  
const router = useRouter()
router.push({
  pathname: '/dashboard',
  query: {key : value},
})

I didn't find how to do it in the docs.

In the app folder, router.push(href: string) accepts as a parameter only the href as a string. If you need query strings, you need to set them yourself, as they show in this example.

In your case, it can be like so:

"use client";

import { useRouter } from "next/navigation";

export default function ExampleClientComponent() {
  const router = useRouter();

  const createQueryString = (name, value) => {
    const params = new URLSearchParams();
    params.set(name, value);

    return params.toString();
  };

  return (
    <button
      onClick={() => {
        router.push("/dashboard" + "?" + createQueryString("key", "value"));
      }}
    >
      Redirect with a query parameter
    </button>
  );
}

You would read it with the searchParams passed to your page component:

// app/dashboard/page.js

export default function Page({ searchParams }) {
  return <div>{searchParams.key}</div>;
}

Or using the useSearchParams function in any client component:

"use client";

import { useSearchParams } from "next/navigation";

export default function Page() {
  const searchParams = useSearchParams();
  return <div>{searchParams.get("key")}</div>;
}

⚠️: query parameters are stings. You can pass multiple at once. But if you need to pass an object to one key, you need to params.set("key", JSON.stringify(value)).
And call JSON.parse on the value before using it on the other side.