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loader-utils

# Methods

## <tt>getOptions</tt>

Recommended way to retrieve the options of a loader invocation:

// inside your loader
const options = loaderUtils.getOptions(this);

1. If `this.query` is a string:
   - Tries to parse the query string and returns a new object
   - Throws if it's not a valid query string
2. If `this.query` is object-like, it just returns `this.query`
3. In any other case, it just returns `null`

Please note: The returned `options` object is read-only. It may be re-used across multiple invocations. If you pass it on to another library, make sure to make a deep copy of it:

const options = Object.assign(
{},
defaultOptions,
loaderUtils.getOptions(this) // it is safe to pass null to Object.assign()
);
// don't forget nested objects or arrays
options.obj = Object.assign({}, options.obj);
options.arr = options.arr.slice();
someLibrary(options);

clone is a good library to make a deep copy of the options.

### Options as query strings

If the loader options have been passed as loader query string (`loader?some&params`), the string is parsed by using `parseQuery`.

## <tt>parseQuery</tt>

Parses a passed string (e.g. `loaderContext.resourceQuery`) as a query string, and returns an object.

const params = loaderUtils.parseQuery(this.resourceQuery); // resource: `file?param1=foo`
if (params.param1 === "foo") {
// do something
}

The string is parsed like this:

-> Error
? -> {}
?flag -> { flag: true }
?+flag -> { flag: true }
?-flag -> { flag: false }
?xyz=test -> { xyz: "test" }
?xyz=1 -> { xyz: "1" } // numbers are NOT parsed
?xyz[]=a -> { xyz: ["a"] }
?flag1&flag2 -> { flag1: true, flag2: true }
?+flag1,-flag2 -> { flag1: true, flag2: false }
?xyz[]=a,xyz[]=b -> { xyz: ["a", "b"] }
?a%2C%26b=c%2C%26d -> { "a,&b": "c,&d" }
?{data:{a:1},isJSON5:true} -> { data: { a: 1 }, isJSON5: true }

## <tt>stringifyRequest</tt>

Turns a request into a string that can be used inside `require()` or `import` while avoiding absolute paths. Use it instead of `JSON.stringify(...)` if you're generating code inside a loader.

Why is this necessary? Since webpack calculates the hash before module paths are translated into module ids, we must avoid absolute paths to ensure consistent hashes across different compilations.

This function:

- resolves absolute requests into relative requests if the request and the module are on the same hard drive
- replaces `\` with `/` if the request and the module are on the same hard drive
- won't change the path at all if the request and the module are on different hard drives
- applies `JSON.stringify` to the result

loaderUtils.stringifyRequest(this, "./test.js");
// "\"./test.js\""
loaderUtils.stringifyRequest(this, ".\\test.js");
// "\"./test.js\""
loaderUtils.stringifyRequest(this, "test");
// "\"test\""
loaderUtils.stringifyRequest(this, "test/lib/index.js");
// "\"test/lib/index.js\""
loaderUtils.stringifyRequest(this, "otherLoader?andConfig!test?someConfig");
// "\"otherLoader?andConfig!test?someConfig\""
loaderUtils.stringifyRequest(this, require.resolve("test"));
// "\"../node_modules/some-loader/lib/test.js\""
loaderUtils.stringifyRequest(this, "C:\\module\\test.js");
// "\"../../test.js\"" (on Windows, in case the module and the request are on the same drive)
loaderUtils.stringifyRequest(this, "C:\\module\\test.js");
// "\"C:\\module\\test.js\"" (on Windows, in case the module and the request are on different drives)
loaderUtils.stringifyRequest(this, "\\\\network-drive\\test.js");
// "\"\\\\network-drive\\\\test.js\"" (on Windows, in case the module and the request are on different drives)

## <tt>urlToRequest</tt>

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"

## <tt>interpolateName</tt>

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 of the resource is in.
- `[emoji]` a random emoji representation of `options.content`
- `[emoji:<length>]` same as above, but with a customizable number of emojis
- `[contenthash]` the hash of `options.content` (Buffer) (by default it's the hex digest of the md5 hash)
- `[<hashType>:contenthash:<digestType>:<length>]` optionally one can configure
  - other `hashType`s, i. e. `sha1`, `md5`, `sha256`, `sha512`
  - other `digestType`s, 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 md5 hash)
- `[<hashType>:hash:<digestType>:<length>]` optionally one can configure
  - other `hashType`s, i. e. `sha1`, `md5`, `sha256`, `sha512`
  - other `digestType`s, 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 = "/app/js/javascript.js"
loaderUtils.interpolateName(loaderContext, "js/[hash].script.[ext]", { content: ... });
// => js/9473fdd0d880a43c21b7778d34872157.script.js
// loaderContext.resourcePath = "/app/js/javascript.js"
loaderUtils.interpolateName(loaderContext, "js/[contenthash].script.[ext]", { content: ... });
// => js/9473fdd0d880a43c21b7778d34872157.script.js
// loaderContext.resourcePath = "/app/page.html"
loaderUtils.interpolateName(loaderContext, "html-[hash:6].html", { content: ... });
// => html-9473fd.html
// loaderContext.resourcePath = "/app/flash.txt"
loaderUtils.interpolateName(loaderContext, "[hash]", { content: ... });
// => c31e9820c001c9c4a86bce33ce43b679
// loaderContext.resourcePath = "/app/img/image.gif"
loaderUtils.interpolateName(loaderContext, "[emoji]", { content: ... });
// => 👍
// loaderContext.resourcePath = "/app/img/image.gif"
loaderUtils.interpolateName(loaderContext, "[emoji:4]", { content: ... });
// => 🙍🏢📤🐝
// loaderContext.resourcePath = "/app/img/image.png"
loaderUtils.interpolateName(loaderContext, "[sha512:hash:base64:7].[ext]", { content: ... });
// => 2BKDTjl.png
// use sha512 hash instead of md5 and with only 7 chars of base64
// loaderContext.resourcePath = "/app/img/myself.png"
// loaderContext.query.name =
loaderUtils.interpolateName(loaderContext, "picture.png");
// => picture.png
// loaderContext.resourcePath = "/app/dir/file.png"
loaderUtils.interpolateName(loaderContext, "[path][name].[ext]?[hash]", { content: ... });
// => /app/dir/file.png?9473fdd0d880a43c21b7778d34872157
// loaderContext.resourcePath = "/app/js/page-home.js"
loaderUtils.interpolateName(loaderContext, "script-[1].[ext]", { regExp: "page-(.*)\\.js", content: ... });
// => script-home.js

## <tt>getHashDigest</tt>

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

- `buffer` the content that should be hashed
- `hashType` one of `sha1`, `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)