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#.js that runs with astro
frosty glenBOT
Yes, you can import a .js file into an Astro component and use the exported values. In your case, you can import the Output constant from your .js file into your index.astro file.
Here's how you can do it:
- First, ensure your
.jsfile is correctly exporting theOutputconstant. Your file should look like this:
let A = 1;
let B = 2;
export const Output = `${A} ${B}`;
- Next, in your
index.astrofile, you can import theOutputconstant. You can then use this constant in your Astro component. Here's an example:
---
import { Output } from './path-to-your-js-file.js';
---
<h1>{Output}</h1>
In this example, the Output constant is used inside the HTML template of the Astro component. Note that when you want to use JavaScript inside the HTML template of an Astro component, you need to wrap it in curly braces.
For more information, you can refer to the Astro documentation on how to write JavaScript expressions in Astro (https://docs.astro.build/en/tutorial/2-pages/3/#write-javascript-expressions-in-astro) and how to use script tags in Astro (https://docs.astro.build/en/guides/client-side-scripts/#using-script-in-astro).
Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:
stable orchid
I dont want to import it everytime the website gets loaded, run once with astro @frosty glen
frosty glenBOT
Let me check the knowledge base for you. One moment! :books:
Astro runs JavaScript at build time, not at runtime. This means that when you import a JavaScript file into an Astro component, the JavaScript code is executed when you build your Astro project, not every time the website is loaded.
However, if you want to run a JavaScript file once when the Astro server starts, you might need to use Node.js builtins. Astro supports Node.js builtins using Node’s newer node: prefix. Here's an example:
---
// Example: import the "fs/promises" builtin from Node.js
import fs from 'node:fs/promises';
const url = new URL('../../package.json', import.meta.url);
const json = await fs.readFile(url, 'utf-8');
const data = JSON.parse(json);
---
<span>Version: {data.version}</span>
In this example, the fs module from Node.js is imported and used to read a file. This code is executed when the Astro server starts, not every time the website is loaded.
Please note that Astro encourages users to avoid Node.js builtins (fs, path, etc.) whenever possible because Astro is compatible with multiple runtimes using adapters (https://docs.astro.build/en/guides/server-side-rendering/), including Deno (https://github.com/denoland/deno-astro-adapter) and Cloudflare Workers (https://docs.astro.build/en/guides/integrations-guide/cloudflare/), which do not support Node builtin modules such as fs.