Creates a cosmiconfig instance ("explorer") configured according to the arguments, and initializes its caches.
#### moduleName
Type: `string`. **Required.**
Your module name. This is used to create the default [`searchPlaces`] and [`packageProp`].
If your [`searchPlaces`] value will include files, as it does by default (e.g. `${moduleName}rc`), your `moduleName` must consist of characters allowed in filenames. That means you should not copy scoped package names, such as `@my-org/my-package`, directly into `moduleName`.
**[`cosmiconfigOptions`] are documented below.**
You may not need them, and should first read about the functions you'll use.
Searches for a configuration file. Returns a Promise that resolves with a [result] or with `null`, if no configuration file is found.
You can do the same thing synchronously with [`explorerSync.search()`].
Let's say your module name is `goldengrahams` so you initialized with `const explorer = cosmiconfig('goldengrahams');`.
Here's how your default [`search()`] will work:
- Starting from `process.cwd()` (or some other directory defined by the `searchFrom` argument to [`search()`]), look for configuration objects in the following places:
1. A `goldengrahams` property in a `package.json` file.
2. A `.goldengrahamsrc` file with JSON or YAML syntax.
3. A `.goldengrahamsrc.json`, `.goldengrahamsrc.yaml`, `.goldengrahamsrc.yml`, `.goldengrahamsrc.js`, `.goldengrahamsrc.ts`, `.goldengrahamsrc.mjs`, or `.goldengrahamsrc.cjs` file. (To learn more about how JS files are loaded, see ["Loading JS modules"].)
4. A `goldengrahamsrc`, `goldengrahamsrc.json`, `goldengrahamsrc.yaml`, `goldengrahamsrc.yml`, `goldengrahamsrc.js`, `goldengrahamsrc.ts`, `goldengrahamsrc.mjs`, or `goldengrahamsrc.cjs` file in the `.config` subdirectory.
5. A `goldengrahams.config.js`, `goldengrahams.config.ts`, `goldengrahams.config.mjs`, or `goldengrahams.config.cjs` file. (To learn more about how JS files are loaded, see ["Loading JS modules"].)
- If at any point a parsable configuration is found, the [`search()`] Promise resolves with its [result] \(or, with [`explorerSync.search()`], the [result] is returned).
- If no configuration object is found, the [`search()`] Promise resolves with `null` (or, with [`explorerSync.search()`], `null` is returned).
- If a configuration object is found *but is malformed* (causing a parsing error), the [`search()`] Promise rejects with that error (so you should `.catch()` it). (Or, with [`explorerSync.search()`], the error is thrown.)
**If you know exactly where your configuration file should be, you can use [`load()`], instead.**
**The search process is highly customizable.**
Use the cosmiconfig options [`searchPlaces`] and [`loaders`] to precisely define where you want to look for configurations and how you want to load them.
#### searchFrom
Type: `string`.
Default: `process.cwd()`.
A filename.
[`search()`] will start its search here.
If the value is a directory, that's where the search starts.
If it's a file, the search starts in that file's directory.
For the [synchronous API](#synchronous-api), the only difference is that `.mjs` files are not included. See ["Loading JS modules"] for more information.
Create your own array to search more, fewer, or altogether different places.
Every item in `searchPlaces` needs to have a loader in [`loaders`] that corresponds to its extension.
(Common extensions are covered by default loaders.)
Read more about [`loaders`] below.
`package.json` is a special value: When it is included in `searchPlaces`, Cosmiconfig will always parse it as JSON and load a property within it, not the whole file.
That property is defined with the [`packageProp`] option, and defaults to your module name.
(YAML is a superset of JSON;which means YAML parsers can parse JSON;which is how extensionless files can be either YAML *or* JSON with only one parser.)
**If you provide a `loaders` object, your object will be *merged* with the defaults.**
So you can override one or two without having to override them all.
**Keys in `loaders`** are extensions (starting with a period), or `noExt` to specify the loader for files *without* extensions, like `.myapprc`.
**Values in `loaders`** are a loader function (described below) whose values are loader functions.
**The most common use case for custom loaders value is to load extensionless `rc` files as strict JSON**, instead of JSON *or* YAML (the default).
To accomplish that, provide the following `loaders` value:
```js
{
noExt: defaultLoaders['.json'];
}
```
If you want to load files that are not handled by the loader functions Cosmiconfig exposes, you can write a custom loader function or use one from NPM if it exists.
**Use cases for custom loader function:**
- Allow configuration syntaxes that aren't handled by Cosmiconfig's defaults, like JSON5, INI, or XML.
- Parse JS files with Babel before deriving the configuration.
**Custom loader functions** have the following signature:
If nested property names within the path include periods, you need to use an array of strings. For example, the value `['configs', 'foo.bar', 'baz']` will get you the `"baz"` value in a `package.json` like this:
If a string includes period but corresponds to a top-level property name, it will not be interpreted as a period-delimited path. For example, the value `'one.two'` will get you the `"three"` value in a `package.json` like this:
```json
{
"one.two": "three",
"one": {
"two": "four"
}
}
```
### stopDir
Type: `string`.
Default: Absolute path to your home directory.
Directory where the search will stop.
### cache
Type: `boolean`.
Default: `true`.
If `false`, no caches will be used.
Read more about ["Caching"](#caching) below.
### transform
Type: `(Result) => Promise<Result> | Result`.
A function that transforms the parsed configuration. Receives the [result].
If using [`search()`] or [`load()`] \(which are async), the transform function can return the transformed result or return a Promise that resolves with the transformed result.
If using `cosmiconfigSync`, [`search()`] or [`load()`], the function must be synchronous and return the transformed result.
The reason you might use this option —instead of simply applying your transform function some other way —is that *the transformed result will be cached*. If your transformation involves additional filesystem I/O or other potentially slow processing, you can use this option to avoid repeating those steps every time a given configuration is searched or loaded.
### ignoreEmptySearchPlaces
Type: `boolean`.
Default: `true`.
By default, if [`search()`] encounters an empty file (containing nothing but whitespace) in one of the [`searchPlaces`], it will ignore the empty file and move on.
If you'd like to load empty configuration files, instead, set this option to `false`.
Why might you want to load empty configuration files?
If you want to throw an error, or if an empty configuration file means something to your program.
## Loading JS modules
Your end users can provide JS configuration files as ECMAScript modules (ESM) under the following conditions:
- You (the cosmiconfig user) use cosmiconfig's [asynchronous API](#asynchronous-api).
- Your end user runs a version of Node that supports ESM ([>=12.17.0](https://nodejs.org/en/blog/release/v12.17.0/), or earlier with the `--experimental-modules` flag).
- Your end user provides an `.mjs` configuration file, or a `.js` file whose nearest parent `package.json` file contains `"type": "module"`. (See [Node's method for determining a file's module system](https://nodejs.org/api/packages.html#packages_determining_module_system).)
With cosmiconfig's [asynchronous API](#asynchronous-api), the default [`searchPlaces`] include `.js`, `.ts`, `.mjs`, and `.cjs` files. Cosmiconfig loads all these file types with the [dynamic `import` function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import#dynamic_imports).
With the [synchronous API](#synchronous-api), JS configuration files are always treated as CommonJS, and `.mjs` files are ignored, because there is no synchronous API for the dynamic `import` function.
## Caching
As of v2, cosmiconfig uses caching to reduce the need for repetitious reading of the filesystem or expensive transforms. Every new cosmiconfig instance (created with `cosmiconfig()`) has its own caches.
To avoid or work around caching, you can do the following:
- Set the `cosmiconfig` option [`cache`] to `false`.
- Use the cache-clearing methods [`clearLoadCache()`], [`clearSearchCache()`], and [`clearCaches()`].
- Create separate instances of cosmiconfig (separate "explorers").
## Differences from [rc](https://github.com/dominictarr/rc)
[rc](https://github.com/dominictarr/rc) serves its focused purpose well. cosmiconfig differs in a few key ways —making it more useful for some projects, less useful for others:
- Looks for configuration in some different places: in a `package.json` property, an rc file, a `.config.js` file, and rc files with extensions.
- Built-in support for JSON, YAML, and CommonJS formats.
- Stops at the first configuration found, instead of finding all that can be found up the directory tree and merging them automatically.
- Options.
- Asynchronous by default (though can be run synchronously).
## Usage for end users
When configuring a tool, you can use multiple file formats and put these in multiple places.
Usually, a tool would mention this in its own README file,
but by default, these are the following places, where `{NAME}` represents the name of the tool:
Please note that this project is released with a [Contributor Code of Conduct](CODE_OF_CONDUCT.md). By participating in this project you agree to abide by its terms.
