# loader-utils ## Methods ### `getOptions` Recommended way to retrieve the options of a loader invocation: ```javascript // 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: ```javascript 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](https://www.npmjs.com/package/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). ### `parseQuery` Parses a passed string (e.g. `loaderContext.resourceQuery`) as a query string, and returns an object. ``` javascript const params = loaderUtils.parseQuery(this.resourceQuery); // resource: `file?param1=foo` if (params.param1 === "foo") { // do something } ``` The string is parsed like this: ``` text -> 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 ```javascript 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. > i Before call `urlToRequest` you need call `isUrlRequest` to ensure it is requestable url ```javascript 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: ```javascript 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. ```javascript 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: ```javascript 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 `~`: ```javascript 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. ```javascript 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` * `[emoji]` a random emoji representation of `options.content` * `[emoji:]` 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 md4 hash) * `[:contenthash::]` optionally one can configure * other `hashType`s, i. e. `sha1`, `md4`, `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 md4 hash) * `[:hash::]` optionally one can configure * other `hashType`s, i. e. `sha1`, `md4`, `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 ``` javascript // 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.gif" loaderUtils.interpolateName(loaderContext, "[emoji]", { content: ... }); // => 👍 // loaderContext.resourcePath = "/absolute/path/to/app/img/image.gif" loaderUtils.interpolateName(loaderContext, "[emoji:4]", { content: ... }); // => 🙍🏢📤🐝 // 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 md4 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` ``` javascript const digestString = loaderUtils.getHashDigest(buffer, hashType, digestType, maxLength); ``` * `buffer` the content that should be hashed * `hashType` one of `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)