Solution to the Asynchronous Parameter Type Error in Next.js 15 Routing

In the development of Next.js 15 applications, when attempting to use asynchronous parameters, type mismatch errors may occur because Next.js has specific expectations for the type structure of the params object.

In a Next.js 15 application, if you want to extract the slug parameter from the params returned as a Promise, the code in page.tsx is as follows:

type tParams = Promise<{ slug: string[] }>;
export default async function Challenge({ params }: { params: tParams }) {
  const { slug } = await params;
  const productID = slug[1];
  // other code here
}

When running npm run build, the following error will appear:

Type error: Type '{ params: { id: string; }; }' does not satisfy the constraint 'PageProps'. Types of property 'params' are incompatible. Type '{ id: string; }' is missing the following properties from type 'Promise': then, catch, finally, [Symbol.toStringTag]

Initially, params was defined as { slug: string[] }. To handle asynchronous behavior, it was changed to Promise<{ slug: string[] }>. However, trying different params type configurations was unsuccessful.

After analysis, it was found that the root cause of the problem is that the original code uses destructuring to handle the asynchronous params object, which may not meet Next.js's requirements and lead to type mismatch errors. As shown in the above error code example, this destructuring method may prevent Next.js from correctly identifying the type of params, thus triggering a type error.

Solutions

Solution 1

Do Not Use Destructured Members of Asynchronous Page Properties

Referring to the migration guide example, instead of using destructuring, directly use props.params to obtain parameters. Modify the code as follows:

type tParams = Promise<{ slug: string[] }>;
export default async function Challenge(props: { params: tParams }) {
  const { slug } = await props.params;
  const productID = slug[1];
  // other code here
}

Solution 2

Handle Asynchronous params Objects Based on Whether async await is Used

• Without using async await:

import { use } from "react";
export default function CategoryDetail({ params }: { params: Promise<{ id: string }> }) {
  const { id } = use(params);
  // ...
}

• When using async await:

export default async function CategoryDetail({ params }: { params: Promise<{ id: string }> }) {
  const { id } = await params;
  // ...
}

Summary and Reflection

When using asynchronous parameters in Next.js 15, be careful to avoid directly destructuring the asynchronous params object, as this can easily lead to type mismatch errors. You can either avoid using destructuring and directly use props.params to obtain parameters or, depending on whether async await is used, use the use function or await to handle the asynchronous params object. In subsequent development, pay special attention to the specific requirements of frameworks like Next.js for object type structures to avoid errors caused by improper type handling.