react/compat as module gives undefined __Hook #4127

GeorgeRadev · 2023-09-04T14:05:33Z

Check if updating to the latest Preact version resolves the issue

Describe the bug
When trying to use vanilla JS and preact/compat
it fails with undefined currentComponent.__hooks
in function getHookState(index, type)
under Firefox and Chromium

To Reproduce
simple code with js modules:

<!DOCTYPE html>
<html>

<head>
  <meta charset="UTF-8" />
  <title>PReact Hello World</title>
</head>

<body>
  <div id="root"></div>

  <script type="importmap">
  {
      "imports": {
        "preact": "https://unpkg.com/[email protected]/dist/preact.mjs",
        "preact/hooks": "https://unpkg.com/[email protected]/hooks/dist/hooks.mjs",
        "react": "https://unpkg.com/[email protected]/compat/dist/compat.mjs",
        "react-dom": "https://unpkg.com/[email protected]/compat/dist/compat.mjs"
      }
  }
  </script>
  <script type="module">
    import React from 'react';
    import ReactDOM from "react-dom";

    function counter() {
      // State to store count value
      const [count, setCount] = React.useState(0);

      // Function to increment count by 1
      const incrementCount = () => {
        // Update state with incremented value
        setCount(count + 1);
      };
      return React.createElement("div", {
        className: "app"
      }, React.createElement("button", {
        onClick: incrementCount
      }, "Click Here"), count);
    }

    const rootElement = document.getElementById('root');
    const element = counter();
    preact.createRoot(rootElement).render(element);
  </script>
</body>

</html>

Steps to reproduce the behavior:

create an html page with the code above and open it in the browser
check the console

Expected behavior
there should not be syntax errors and the code should render a preact component

marvinhagemeister · 2023-09-04T15:17:25Z

@GeorgeRadev Component functions cannot be called directly. They expect to be called in the context of the rendering framework. If you just call them outside that the whole rendering context needed for hooks and things will not be present, hence the error.

function App() {
  return <h1>hello world</h1>
}

// BAD: Don't do this, component is called eagerly outside of
// the rendering context.
render(App(), document.getElementById("app"));

// CORRECT
render(<App />, document.getElementById("app"));

Applying the fix to your snippet:

-    const element = counter();
-    preact.createRoot(rootElement).render(element);
+    const element = React.createElement(counter, null);
+    ReactDom.render(element, rootElement); // React v18 APIs are not supported in compat

FYI: You can also simplify your import map quite a bit by going with esm.sh:

 {
   "imports": {
    "preact": "https://esm.sh/[email protected]",
    "preact/": "https://esm.sh/[email protected]/",
    "react": "https://esm.sh/[email protected]/compat",
    "react-dom": "https://esm.sh/[email protected]/compat"
  }
}

Also you can enable helpful debug messages that warn you of issues like the one you ran into by using preact/debug:

// Import this at the top of your JS file
import "preact/debug";

GeorgeRadev · 2023-09-04T15:37:11Z

Thank you @marvinhagemeister,
The fastest, accurate and understandable response.
Now it make sense that the function needs to be executed when the rendering is happening, the result of it has no use bore that.
Thank you once again

marvinhagemeister closed this as completed Sep 4, 2023

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react/compat as module gives undefined __Hook #4127

react/compat as module gives undefined __Hook #4127

GeorgeRadev commented Sep 4, 2023

marvinhagemeister commented Sep 4, 2023 •

edited

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GeorgeRadev commented Sep 4, 2023

react/compat as module gives undefined __Hook #4127

react/compat as module gives undefined __Hook #4127

Comments

GeorgeRadev commented Sep 4, 2023

marvinhagemeister commented Sep 4, 2023 • edited Loading

GeorgeRadev commented Sep 4, 2023

marvinhagemeister commented Sep 4, 2023 •

edited

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