How can I write Javascript function in React JSX?

I got this error called "TypeError: Cannot read properties of undefined (reading ‘split’)"
I am aware of where the error came from, but I don’t know how to put the right code in it.
I am using Next.js and TailwindCSS 🙂

The code below is what I wrote:

 {productCategories.map(m => (
          <li className="group relative hover:cursor-pointer" key={m.databaseId} onClick={() => onClickParentMenu(m.databaseId)}>
            <Link passHref href={`/${m.url.split('/').splice(2, 2).join('/')}`}>
              <a className={`${router.asPath === '/' ? 'hover:text-white' : 'text-black hover:opacity-50'} ${clickedParentId === m.databaseId && 'font-bold'}`}>{m.name}</a>
            </Link>
            <ul className="absolute hidden text-gray-500 pt-4 group-hover:block">
              {m.children.nodes.map(c => (
                <li key={c.databaseId} className="w-auto whitespace-nowrap shadow-md bg-white hover:bg-gray-100 hover:text-black py-2 px-4 block" onClick={() => onClickChildMenu(c.databaseId)}>
                  <Link passHref href={`/product-category/${m.slug}/${c.slug}`}>
                    <a className={`${clickedChildId === c.databaseId && 'font-bold'}`}>{c.name}</a>
                  </Link>
                </li>
              ))}
            </ul>
          </li>
        ))}

The code that makes the error:

 <Link passHref href={`/${m.url.split('/').splice(2, 2).join('/')}`}>

>Solution :

Inside the same file of your component, you can define:

function extractURL(category) {
  if (!category.url) {
    // handle the problem somehow and return an appropriate value
  }
  return `/${category.url.split('/').splice(2, 2).join('/')}`;
}

And call it like:

<Link passHref href={extractURL(m)}>...</Link>