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Update 04-$effect.md #14881

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10 changes: 6 additions & 4 deletions documentation/docs/02-runes/04-$effect.md
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Original file line number Diff line number Diff line change
Expand Up @@ -149,15 +149,15 @@ In rare cases, you may need to run code _before_ the DOM updates. For this we ca
import { tick } from 'svelte';

let div = $state();
let messages = $state([]);

// ...
let messages = $state(["ddd"]);

$effect.pre(() => {
if (!div) return; // not yet mounted

// reference `messages` array length so that this code re-runs whenever it changes
messages.length;
// No need this line this for old svelte syntax you have to refrence like array = array.push(x)
//messages.length;


// autoscroll when new messages are added
if (div.offsetHeight + div.scrollTop > div.scrollHeight - 20) {
Expand All @@ -173,6 +173,8 @@ In rare cases, you may need to run code _before_ the DOM updates. For this we ca
<p>{message}</p>
{/each}
</div>

<input bind:value={messages} />
```

Apart from the timing, `$effect.pre` works exactly like `$effect`.
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