docs: clarify MIME type changes when migrating from Express 4 to 5 #1903
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bjohansebas
reviewed
May 15, 2025
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@bjohansebas I have added it back |
bjohansebas
reviewed
May 17, 2025
en/guide/migrating-5.md
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| @@ -345,6 +345,8 @@ The `router.param(fn)` signature was used for modifying the behavior of the `rou | |||
| In Express 5, `mime` is no longer an exported property of the `static` field. | |||
| Use the [`mime-types` package](https://github.com/jshttp/mime-types) to work with MIME type values. | |||
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| **Important:** This change affects not only direct usage of `express.static.mime` but also other Express methods that rely on MIME type detection, such as `res.sendFile()`. For example, JavaScript files (.js) will now be served with the MIME type "text/javascript" instead of "application/javascript" as in Express 4. Other file types may also have different MIME types than before. If your application depends on specific MIME types, you should test thoroughly after upgrading. | |||
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I would recommend listing the MIME types that changed, instead of saying “try which ones changed.”
bjohansebas
reviewed
May 17, 2025
en/guide/migrating-5.md
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| <h4 id="res.sendfile">res.sendfile()</h4> | ||
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| The `res.sendfile()` function has been replaced by a camel-cased version `res.sendFile()` in Express 5. | ||
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| **Note:** In Express 5, `res.sendFile()` uses the `mime-types` package for MIME type detection, which may return different Content-Type values than Express 4 did. For example, JavaScript files (.js) will now be served with "text/javascript" instead of "application/javascript". If your application depends on specific MIME types, you should test thoroughly after upgrading. |
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@bjohansebas I have done the changes you asked me to do. |
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This PR improves the Express 5 migration guide by documenting an important change in MIME type handling that affects users migrating from Express 4 to Express 5.
Issue #1880
When migrating from Express 4 to Express 5, we discovered that JavaScript files served via
res.sendFile()now return a Content-Type of "text/javascript" instead of the previous "application/javascript". This change occurs because Express 5 switched from its internal MIME type handling to themime-typespackage.Changes
express.static.mimesection explaining that this change affects other methods likeres.sendFile()res.sendfile()section warning about potential Content-Type differencesThese documentation improvements will help users understand and prepare for potential MIME type differences when upgrading to Express 5, even if they weren't directly using
express.static.mime.Developer's Certificate of Origin 1.1 is acknowledged and agreed to.