Next.js is refusing to render an array of HTML elements

Question

Next.js is refusing to render an array of HTML elements

Consider this scenario where I have a block of code in TypeScript that attempts to create and display a list of elements. Here is a sample implementation:

   const MenuList = ():ReactElement => {

    const router = useRouter(),
liElements:any = [];
console.log(navRoutes)

useEffect(() => {
    for(let elem in navRoutes){
        const htmlElement = (
            <>
                <li>
                    <a
                        href={navRoutes[elem].href}
                    >
                        {navRoutes[elem].name}
                    </a>
                </li>
            </>
        )
        liElements.push(htmlElement)
    }
    
    
})
console.log(liElements,'dups')
return (
    <>
        <ul className={''}>
    {liElements.map((elem:any) => elem)}
        </ul>
    </>
)

}

export { MenuList }`

I wonder why the statement "{liElements.map((elem:any) => elem)}" doesn't render any elements?

javascript html css typescript next.js

Answer 1

Answer №1

The issue lies in the incorrect usage of the useEffect hook. However, in this particular scenario, the use of it is unnecessary. You can simply write the code without it:

const MenuList = (): ReactElement => {

    const router = useRouter(), liElements: any = [];

    for (let elem in navRoutes) {
        const htmlElement = (
            <>
                <li>
                    <a
                        href={navRoutes[elem].href}
                    >
                        {navRoutes[elem].name}
                    </a>
                </li>
            </>
        )
        liElements.push(htmlElement)
    }

    return (
        <>
            <ul className={''}>
                {liElements.map((elem: any) => elem)}
            </ul>
        </>
    )
}

If you're curious about when and how to use the useEffect hook:

Use it to fetch data from an API (or perform other asynchronous operations) and store the result in state (e.g., using useState). It is important not to modify anything outside the scope of useEffect (as you are currently doing), as it can lead to unpredictable behavior. If you want to save the result of useEffect, use useState.
Use it to modify HTML outside of the React component (e.g., setting the meta title). This is useful because you can execute code inside useEffect only once or specify when it should be executed using dependencies as the second argument. Keep in mind that your component function can be called multiple times, even during a single rendering.

By the way, I'm not sure what navRoutes refers to in your code :/

Answer 2

The issue lies in the incorrect usage of the useEffect hook. However, in this particular scenario, the use of it is unnecessary. You can simply write the code without it:

const MenuList = (): ReactElement => {

    const router = useRouter(), liElements: any = [];

    for (let elem in navRoutes) {
        const htmlElement = (
            <>
                <li>
                    <a
                        href={navRoutes[elem].href}
                    >
                        {navRoutes[elem].name}
                    </a>
                </li>
            </>
        )
        liElements.push(htmlElement)
    }

    return (
        <>
            <ul className={''}>
                {liElements.map((elem: any) => elem)}
            </ul>
        </>
    )
}

If you're curious about when and how to use the useEffect hook:

Use it to fetch data from an API (or perform other asynchronous operations) and store the result in state (e.g., using useState). It is important not to modify anything outside the scope of useEffect (as you are currently doing), as it can lead to unpredictable behavior. If you want to save the result of useEffect, use useState.
Use it to modify HTML outside of the React component (e.g., setting the meta title). This is useful because you can execute code inside useEffect only once or specify when it should be executed using dependencies as the second argument. Keep in mind that your component function can be called multiple times, even during a single rendering.

By the way, I'm not sure what navRoutes refers to in your code :/

Next.js is refusing to render an array of HTML elements

Answer №1

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