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About

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All MIME type mappings are based on mime-db (2023-02-17). For filesize reasons only a small selected number of vendor MIME types (aka */vnd.*) are included. Most of the omitted ones are fairly obscure anyway, so likely not problematic...

Additionally, this package defines some MIME types not included in the original DB, as well as some preference overrides.

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Installation

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Dependencies

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API

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This package exposes a MIME_TYPES object which provides mappings from file extensions to MIME types. For each extension one or more MIME types are provided, with the default type always in first position.

import { MIME_TYPES } from "@thi.ng/mime";

MIME_TYPES.mp3
// [ 'audio/mpeg', 'audio/mp3' ]

MIME_TYPES.jpg
// [ 'image/jpeg' ]

MIME_TYPES.jpeg
// [ 'image/jpeg' ]

Determining MIME type from file extension

To simplify lookup and support a fallback type, the package has preferredType() function:

import { preferredType } from "@thi.ng/mime";

preferredType("mp3")
// "audio/mpeg"

// unknown file extension w/ default fallback type
preferredType("foo")
// "application/octet-stream"

// unknown file extension w/ given fallback type
preferredType("foo", "text/plain")
// "text/plain"

Determining file extension from MIME type

Reverse lookups are possible too, using preferredExtension() (also supports fallback):

import { preferredExtension } from "@thi.ng/mime";

preferredExtension("image/svg+xml");
// "svg"

preferredExtension("image/foo");
// "bin" (default fallback)

preferredExtension("image/foo", "dat");
// "dat" (custom fallback)

Checking if MIME type is compressible

The original mime-db includes information if a MIME type is compressible (gzippable). This information can be obtained via isCompressible(). Note: Some of these decisions seem to be questionable/wrong (e.g. many plain text formats are marked as false), but taken here as provided...

import { isCompressible } from "@thi.ng/mime";

isCompressible("text/javascript");
// true

isCompressible(preferredType("mp4"))
// false

Conversion from mime-db

  1. Download the latest version of mime-db's JSON index and save it to [packages/mime/]tools/mime-db.json
  2. Run the following command to build an up-to-date index (assumes the umbrella repo has been pre-built already). Output will always be be written to src/generated.ts.
# from the thi.ng/umbrella repo root
(cd packages/mime && yarn tool:convert)

Additional configuration options are available in the tools/convert.ts script.