loader-utils

What is loader-utils?

The loader-utils package provides utility functions for use with webpack loaders. It offers a variety of helper methods to make writing loaders easier and more standardized. These utilities include parsing query strings, hashing, getting options from loaders, and more.

What are loader-utils's main functionalities?

getOptions

This function is used to parse the options passed to a loader. It simplifies the process of handling loader options within a webpack configuration.

const loaderUtils = require('loader-utils');
const options = loaderUtils.getOptions(this);

stringifyRequest

This method helps to convert a module request into a string that can be used inside of a loader. It's useful for ensuring that the request is correctly formatted and can be resolved by webpack.

const loaderUtils = require('loader-utils');
const stringifiedRequest = loaderUtils.stringifyRequest(this, require.resolve('./file.js'));

getHashDigest

This utility generates a hash digest of the given content. It's commonly used for cache busting or to generate unique identifiers for file contents.

const loaderUtils = require('loader-utils');
const hashDigest = loaderUtils.getHashDigest(Buffer.from('some content'), 'sha512', 'hex', 7);

interpolateName

This function allows for the creation of a custom filename based on placeholders and content. It's often used in file-loader and url-loader to generate names based on the file content.

const loaderUtils = require('loader-utils');
const interpolatedName = loaderUtils.interpolateName(this, '[name]_[hash].[ext]', { content: source });

Other packages similar to loader-utils

schema-utils

Schema-utils validates options for webpack loaders and plugins against a JSON Schema. It is similar to loader-utils in that it helps with managing loader options, but it focuses on validation rather than utility functions.

file-loader

File-loader resolves import/require() on a file into a url and emits the file into the output directory. It's similar to loader-utils' interpolateName feature but is a standalone loader that focuses on file handling.

url-loader

Url-loader works like file-loader but can return a Data URL if the file is smaller than a byte limit. It shares some functionality with loader-utils, particularly in generating filenames and paths.

README

loader-utils

Methods

urlToRequest

Converts some resource URL to a webpack module request.

i Before call urlToRequest you need call isUrlRequest to ensure it is requestable url

const url = "path/to/module.js";

if (loaderUtils.isUrlRequest(url)) {
  // Logic for requestable url
  const request = loaderUtils.urlToRequest(url);
} else {
  // Logic for not requestable url
}

Simple example:

const url = "path/to/module.js";
const request = loaderUtils.urlToRequest(url); // "./path/to/module.js"

Module URLs

Any URL containing a ~ will be interpreted as a module request. Anything after the ~ will be considered the request path.

const url = "~path/to/module.js";
const request = loaderUtils.urlToRequest(url); // "path/to/module.js"

Root-relative URLs

URLs that are root-relative (start with /) can be resolved relative to some arbitrary path by using the root parameter:

const url = "/path/to/module.js";
const root = "./root";
const request = loaderUtils.urlToRequest(url, root); // "./root/path/to/module.js"

To convert a root-relative URL into a module URL, specify a root value that starts with ~:

const url = "/path/to/module.js";
const root = "~";
const request = loaderUtils.urlToRequest(url, root); // "path/to/module.js"

interpolateName

Interpolates a filename template using multiple placeholders and/or a regular expression. The template and regular expression are set as query params called name and regExp on the current loader's context.

const interpolatedName = loaderUtils.interpolateName(
  loaderContext,
  name,
  options
);

The following tokens are replaced in the name parameter:

• [ext] the extension of the resource
• [name] the basename of the resource
• [path] the path of the resource relative to the context query parameter or option.
• [folder] the folder the resource is in
• [query] the queryof the resource, i.e. ?foo=bar
• [contenthash] the hash of options.content (Buffer) (by default it's the hex digest of the xxhash64 hash)
• [<hashType>:contenthash:<digestType>:<length>] optionally one can configure
  • other hashTypes, i. e. xxhash64, sha1, md4 (wasm version), native-md4 (crypto module version), md5, sha256, sha512
  • other digestTypes, i. e. hex, base26, base32, base36, base49, base52, base58, base62, base64
  • and length the length in chars
• [hash] the hash of options.content (Buffer) (by default it's the hex digest of the xxhash64 hash)
• [<hashType>:hash:<digestType>:<length>] optionally one can configure
  • other hashTypes, i. e. xxhash64, sha1, md4 (wasm version), native-md4 (crypto module version), md5, sha256, sha512
  • other digestTypes, i. e. hex, base26, base32, base36, base49, base52, base58, base62, base64
  • and length the length in chars
• [N] the N-th match obtained from matching the current file name against options.regExp

In loader context [hash] and [contenthash] are the same, but we recommend using [contenthash] for avoid misleading.

Examples

// loaderContext.resourcePath = "/absolute/path/to/app/js/javascript.js"
loaderUtils.interpolateName(loaderContext, "js/[hash].script.[ext]", { content: ... });
// => js/9473fdd0d880a43c21b7778d34872157.script.js

// loaderContext.resourcePath = "/absolute/path/to/app/js/javascript.js"
// loaderContext.resourceQuery = "?foo=bar"
loaderUtils.interpolateName(loaderContext, "js/[hash].script.[ext][query]", { content: ... });
// => js/9473fdd0d880a43c21b7778d34872157.script.js?foo=bar

// loaderContext.resourcePath = "/absolute/path/to/app/js/javascript.js"
loaderUtils.interpolateName(loaderContext, "js/[contenthash].script.[ext]", { content: ... });
// => js/9473fdd0d880a43c21b7778d34872157.script.js

// loaderContext.resourcePath = "/absolute/path/to/app/page.html"
loaderUtils.interpolateName(loaderContext, "html-[hash:6].html", { content: ... });
// => html-9473fd.html

// loaderContext.resourcePath = "/absolute/path/to/app/flash.txt"
loaderUtils.interpolateName(loaderContext, "[hash]", { content: ... });
// => c31e9820c001c9c4a86bce33ce43b679

// loaderContext.resourcePath = "/absolute/path/to/app/img/image.png"
loaderUtils.interpolateName(loaderContext, "[sha512:hash:base64:7].[ext]", { content: ... });
// => 2BKDTjl.png
// use sha512 hash instead of xxhash64 and with only 7 chars of base64

// loaderContext.resourcePath = "/absolute/path/to/app/img/myself.png"
// loaderContext.query.name =
loaderUtils.interpolateName(loaderContext, "picture.png");
// => picture.png

// loaderContext.resourcePath = "/absolute/path/to/app/dir/file.png"
loaderUtils.interpolateName(loaderContext, "[path][name].[ext]?[hash]", { content: ... });
// => /app/dir/file.png?9473fdd0d880a43c21b7778d34872157

// loaderContext.resourcePath = "/absolute/path/to/app/js/page-home.js"
loaderUtils.interpolateName(loaderContext, "script-[1].[ext]", { regExp: "page-(.*)\\.js", content: ... });
// => script-home.js

// loaderContext.resourcePath = "/absolute/path/to/app/js/javascript.js"
// loaderContext.resourceQuery = "?foo=bar"
loaderUtils.interpolateName(
  loaderContext,
  (resourcePath, resourceQuery) => {
    // resourcePath - `/app/js/javascript.js`
    // resourceQuery - `?foo=bar`

    return "js/[hash].script.[ext]";
  },
  { content: ... }
);
// => js/9473fdd0d880a43c21b7778d34872157.script.js

getHashDigest

const digestString = loaderUtils.getHashDigest(
  buffer,
  hashType,
  digestType,
  maxLength
);

• buffer the content that should be hashed
• hashType one of xxhash64, sha1, md4, md5, sha256, sha512 or any other node.js supported hash type
• digestType one of hex, base26, base32, base36, base49, base52, base58, base62, base64
• maxLength the maximum length in chars

License

MIT (http://www.opensource.org/licenses/mit-license.php)

Changelog

3.2.0 (2021-11-11)

Features

• hash uniformity for base digests (451858b)