I have a header navigation component that renders navigation from two parts of a JSON response.

The navigation renders correctly but I am getting the: 'Each child in a list should have a unique "key" prop error' even though from what I can see I do have a key for each child element.

The Id from both map calls will be completely unique.

This is the complete code for the component so far:

import React, { useContext } from 'react';
import { Link } from "react-router-dom";
import { HeaderContext } from '../context/headerContext';

const renderToplevelPages = (toplevelPages) => {
    return toplevelPages.map(({ PageUrl, NavLinkText, Id, SubNavMenuItems }) => (
        <li key={Id}><Link to={PageUrl}>{NavLinkText}</Link>
            {SubNavMenuItems && <ul>{renderToplevelPages(SubNavMenuItems)}</ul>}
        </li>
    ));
};

function Header() {

    const headerData = useContext(HeaderContext);

    return (
        <nav>
            <Link to="/">Logo here</Link>
            {headerData
                ? <ul>
                    <li>
                        <Link to={headerData.Menu.PageUrl}>Menu</Link>
                        <ul>
                            {headerData.Menu.Categories.map(categoryItem => (
                                <li key={categoryItem.Id}><Link to={categoryItem.CategoryUrl}>{categoryItem.CategoryName}</Link></li>
                            ))}
                        </ul>
                    </li>
                    <li>
                        <a className="navbar-icon fa-user snipcart-customer-signin">Login/Register</a>
                    </li>
                    {renderToplevelPages(headerData.TopLevelPages)}
                </ul>
                : <div></div>
            }
        </nav >
    )
}

export default Header;

CodePudding user response：

You're missing a key here:

 <li>
     <Link to={headerData.Menu.PageUrl}>Menu</Link>
        ....                
 </li>

and here:

<li>
    <a className="navbar-icon fa-user snipcart-customer-signin">Login/Register</a>
</li>

Just because they're not part of a call to Array.map, they're still children of the parent <ul> so they need a key.

If that doesn't fix it, perhaps your Ids aren't correct - I suggest you check them by rendering the Id instead of e.g. CategoryName.