docs: fixes relating to `bind:files` & note on `FileList` API ()

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brunnerh 6 months ago committed by GitHub
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@ -1,4 +1,4 @@
---
---
title: Bindings
---
@ -42,14 +42,14 @@ Numeric input values are coerced; even though `input.value` is a string as far a
<input type="range" bind:value={num} />
```
On `<input>` elements with `type="file"`, you can use `bind:files` to get the [`FileList` of selected files](https://developer.mozilla.org/en-US/docs/Web/API/FileList). When you want to update the files programmatically, you always need to use a `FileList` object.
On `<input>` elements with `type="file"`, you can use `bind:files` to get the [`FileList` of selected files](https://developer.mozilla.org/en-US/docs/Web/API/FileList). When you want to update the files programmatically, you always need to use a `FileList` object. Currently `FileList` objects cannot be constructed directly, so you need to create a new [`DataTransfer`](https://developer.mozilla.org/en-US/docs/Web/API/DataTransfer) object and get `files` from there.
```svelte
<script>
let files = $state();
function clear() {
files = new FileList(); // null or undefined doesn't work
files = new DataTransfer().files; // null or undefined does not work
}
</script>
@ -58,6 +58,10 @@ On `<input>` elements with `type="file"`, you can use `bind:files` to get the [`
<button onclick={clear}>clear</button>
```
`FileList` objects also cannot be modified, so if you want to e.g. delete a single file from the list, you need to create a new `DataTransfer` object and add the files you want to keep.
> `DataTransfer` may not be available in server-side JS runtimes. Leaving the state that is bound to `files` uninitialized prevents potential errors if components are server-side rendered.
If you're using `bind:` directives together with `on` event attributes, the binding will always fire before the event attribute.
```svelte

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