Error in svelte.config.js Syntax Error: Cannot use import statement outside a module

I setting up svelte.config.js like code below:

import preprocess from 'svelte-preprocess';const config = {  preprocess: preprocess(),};export default config;

Suddenly, my Svelte codes keep getting error Error in svelte.config.js SyntaxError: Cannot use import statement outside a module

How to fix this issue? But I still be able to run the project using npm