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38 lines
2.1 KiB
38 lines
2.1 KiB
# Determine the Encoding of a HTML Byte Stream |
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This package implements the HTML Standard's [encoding sniffing algorithm](https://html.spec.whatwg.org/multipage/syntax.html#encoding-sniffing-algorithm) in all its glory. The most interesting part of this is how it pre-scans the first 1024 bytes in order to search for certain `<meta charset>`-related patterns. |
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```js |
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const htmlEncodingSniffer = require("html-encoding-sniffer"); |
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const fs = require("fs"); |
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const htmlBuffer = fs.readFileSync("./html-page.html"); |
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const sniffedEncoding = htmlEncodingSniffer(htmlBuffer); |
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``` |
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The returned value will be a canonical [encoding name](https://encoding.spec.whatwg.org/#names-and-labels) (not a label). You might then combine this with the [whatwg-encoding](https://github.com/jsdom/whatwg-encoding) package to decode the result: |
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```js |
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const whatwgEncoding = require("whatwg-encoding"); |
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const htmlString = whatwgEncoding.decode(htmlBuffer, sniffedEncoding); |
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``` |
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## Options |
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You can pass two potential options to `htmlEncodingSniffer`: |
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```js |
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const sniffedEncoding = htmlEncodingSniffer(htmlBuffer, { |
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transportLayerEncodingLabel, |
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defaultEncoding |
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}); |
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``` |
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These represent two possible inputs into the [encoding sniffing algorithm](https://html.spec.whatwg.org/multipage/syntax.html#encoding-sniffing-algorithm): |
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- `transportLayerEncodingLabel` is an encoding label that is obtained from the "transport layer" (probably a HTTP `Content-Type` header), which overrides everything but a BOM. |
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- `defaultEncoding` is the ultimate fallback encoding used if no valid encoding is supplied by the transport layer, and no encoding is sniffed from the bytes. It defaults to `"windows-1252"`, as recommended by the algorithm's table of suggested defaults for "All other locales" (including the `en` locale). |
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## Credits |
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This package was originally based on the excellent work of [@nicolashenry](https://github.com/nicolashenry), [in jsdom](https://github.com/tmpvar/jsdom/blob/16fd85618f2705d181232f6552125872a37164bc/lib/jsdom/living/helpers/encoding.js). It has since been pulled out into this separate package.
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