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Add a warning to the JS Hook documentation for changing phx-hook #3509

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Add a warning to the JS Hook documentation for changing phx-hook #3509

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28 changes: 28 additions & 0 deletions guides/client/js-interop.md
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Expand Up @@ -200,6 +200,34 @@ let liveSocket = new LiveSocket("/live", Socket, {hooks: Hooks, ...})

*Note*: when using `phx-hook`, a unique DOM ID must always be set.

> #### Warning {: .warning}
>
> Hooks cannot be added dynamically on an element. For example:
> ```heex
> <div id="my-hook" phx-hook={if @hook_enabled, do: "MyHook"} />
> ```
>
> In this case, if `@hook_enabled` starts as `true`, then the hook will work as
> intended. However, if the value starts as `false` and changes from `false` to `true`,
> the hook will never be initialized, and therefore `mounted` will never be called.
>
> To achieve the desired effect, the hook should always be set, and an attribute on
> the DOM element can be checked in the `updated` callback to toggle the state of
> the hook.
>
> ```heex
> <div id="my-hook" phx-hook="MyHook" data-hook-enabled={to_string(@hook_enabled)} />
> ```
> ```javascript
> hooks.MyHook = {
> updated: {
> if (this.el.getAttribute("data-hook-enabled") !== "false")) {

@kevinschweikert kevinschweikert Dec 5, 2024

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Suggested change
> if (this.el.getAttribute("data-hook-enabled") !== "false")) {
> if (this.el.dataset.hookEnabled !== "false") {

@Neophen Neophen Feb 4, 2025

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i prefer "data-hook-enabled" for the fact being is much easier to search for it globally. There is no benefit of one over the other.

> this.el.innerHTML = "MyHook is enabled";
> }
> }
> }
> ```

For integration with client-side libraries which require a broader access to full
DOM management, the `LiveSocket` constructor accepts a `dom` option with an
`onBeforeElUpdated` callback. The `fromEl` and `toEl` DOM nodes are passed to the
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