Svelte warns of potential undefined Variable when using "bind:this={}"

Whenever I attempt to utilize the bind:this attribute in Svelte, I encounter this message in vscode:

'cardGroup' is possibly 'undefined'.js(18048)

Upon execution, the following error arises:

TypeError: Cannot read properties of undefined (reading 'childNodes')

Initially, I was working in Typescript and received an error indicating that the bound variable was not declared prior to usage.

Below is the script causing the issue:

    let cardGroup;
    let cardContainers = cardGroup.childNodes;
    console.log(cardContainers.length);

Here's the corresponding HTML:

<div class="cardGroup" bind:this={cardGroup}>
    [content]
</div>

Although it's likely that I am overlooking something, I have not come across any information on this binding that isn't performing exactly as I am trying to achieve, as far as I can determine.

javascripttypescriptsvelte

Answer №1

I have identified the issue. To utilize the bind:this feature in Svelte, you must utilize the onMount function to assign it.

Below is the solution that is currently working for me (converted back to Typescript)

    import { onMount } from 'svelte';
    let cardGroup: HTMLDivElement;
    let cardContainers: NodeListOf<ChildNode>;
    onMount(() => {
        cardContainers = cardGroup.childNodes;
        console.log(cardContainers.length);
    });

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