loader-utils
Methods
getOptions
Recommended way to retrieve the options of a loader invocation:
// inside your loader
const options = loaderUtils.getOptions(this);
- 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
- If
this.query
is object-like, it just returnsthis.query
- 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(
{},
loaderUtils.getOptions(this), // it is safe to pass null to Object.assign()
defaultOptions
);
// 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¶ms
), the string is parsed by using parseQuery
.
parseQuery
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 }
stringifyRequest
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)
urlToRequest
Converts some resource URL to a webpack module request.
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 thecontext
query parameter or option.[folder]
the folder of the resource is in.[emoji]
a random emoji representation ofoptions.content
[emoji:<length>]
same as above, but with a customizable number of emojis[hash]
the hash ofoptions.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
- other
[N]
the N-th match obtained from matching the current file name againstoptions.regExp
Examples
// loaderContext.resourcePath = "/app/js/javascript.js"
loaderUtils.interpolateName(loaderContext, "js/[hash].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: ... });
// => π
// loaderContext.resourcePath = "/app/img/image.gif"
loaderUtils.interpolateName(loaderContext, "[emoji:4]", { content: ... });
// => ππ’π€π
// 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
getHashDigest
const digestString = loaderUtils.getHashDigest(buffer, hashType, digestType, maxLength);
buffer
the content that should be hashedhashType
one ofsha1
,md5
,sha256
,sha512
or any other node.js supported hash typedigestType
one ofhex
,base26
,base32
,base36
,base49
,base52
,base58
,base62
,base64
maxLength
the maximum length in chars