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							301 lines
						
					
					
						
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				# resolve <sup>[![Version Badge][2]][1]</sup> | 
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implements the [node `require.resolve()` algorithm](https://nodejs.org/api/modules.html#modules_all_together) such that you can `require.resolve()` on behalf of a file asynchronously and synchronously | 
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 | 
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[![github actions][actions-image]][actions-url] | 
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[![coverage][codecov-image]][codecov-url] | 
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[![dependency status][5]][6] | 
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[![dev dependency status][7]][8] | 
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[![License][license-image]][license-url] | 
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[![Downloads][downloads-image]][downloads-url] | 
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 | 
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[![npm badge][11]][1] | 
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 | 
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# example | 
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 | 
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asynchronously resolve: | 
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 | 
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```js | 
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var resolve = require('resolve/async'); // or, require('resolve') | 
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resolve('tap', { basedir: __dirname }, function (err, res) { | 
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    if (err) console.error(err); | 
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    else console.log(res); | 
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}); | 
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``` | 
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 | 
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``` | 
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$ node example/async.js | 
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/home/substack/projects/node-resolve/node_modules/tap/lib/main.js | 
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``` | 
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 | 
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synchronously resolve: | 
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 | 
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```js | 
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var resolve = require('resolve/sync'); // or, `require('resolve').sync | 
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var res = resolve('tap', { basedir: __dirname }); | 
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console.log(res); | 
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``` | 
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 | 
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``` | 
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$ node example/sync.js | 
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/home/substack/projects/node-resolve/node_modules/tap/lib/main.js | 
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``` | 
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 | 
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# methods | 
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 | 
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```js | 
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var resolve = require('resolve'); | 
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var async = require('resolve/async'); | 
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var sync = require('resolve/sync'); | 
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``` | 
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 | 
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For both the synchronous and asynchronous methods, errors may have any of the following `err.code` values: | 
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 | 
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- `MODULE_NOT_FOUND`: the given path string (`id`) could not be resolved to a module | 
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- `INVALID_BASEDIR`: the specified `opts.basedir` doesn't exist, or is not a directory | 
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- `INVALID_PACKAGE_MAIN`: a `package.json` was encountered with an invalid `main` property (eg. not a string) | 
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 | 
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## resolve(id, opts={}, cb) | 
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Asynchronously resolve the module path string `id` into `cb(err, res [, pkg])`, where `pkg` (if defined) is the data from `package.json`. | 
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options are: | 
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* opts.basedir - directory to begin resolving from | 
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* opts.package - `package.json` data applicable to the module being loaded | 
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* opts.extensions - array of file extensions to search in order | 
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 | 
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* opts.includeCoreModules - set to `false` to exclude node core modules (e.g. `fs`) from the search | 
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 | 
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* opts.readFile - how to read files asynchronously | 
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 | 
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* opts.isFile - function to asynchronously test whether a file exists | 
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* opts.isDirectory - function to asynchronously test whether a file exists and is a directory | 
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 | 
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* opts.realpath - function to asynchronously resolve a potential symlink to its real path | 
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 | 
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* `opts.readPackage(readFile, pkgfile, cb)` - function to asynchronously read and parse a package.json file | 
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  * readFile - the passed `opts.readFile` or `fs.readFile` if not specified | 
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  * pkgfile - path to package.json | 
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  * cb - callback | 
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 | 
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* `opts.packageFilter(pkg, pkgfile, dir)` - transform the parsed package.json contents before looking at the "main" field | 
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  * pkg - package data | 
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  * pkgfile - path to package.json | 
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  * dir - directory that contains package.json | 
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 | 
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* `opts.pathFilter(pkg, path, relativePath)` - transform a path within a package | 
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  * pkg - package data | 
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  * path - the path being resolved | 
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  * relativePath - the path relative from the package.json location | 
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  * returns - a relative path that will be joined from the package.json location | 
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 | 
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* opts.paths - require.paths array to use if nothing is found on the normal `node_modules` recursive walk (probably don't use this) | 
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 | 
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  For advanced users, `paths` can also be a `opts.paths(request, start, opts)` function | 
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    * request - the import specifier being resolved | 
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    * start - lookup path | 
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    * getNodeModulesDirs - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution | 
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    * opts - the resolution options | 
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 | 
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* `opts.packageIterator(request, start, opts)` - return the list of candidate paths where the packages sources may be found (probably don't use this) | 
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    * request - the import specifier being resolved | 
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    * start - lookup path | 
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    * getPackageCandidates - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution | 
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    * opts - the resolution options | 
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 | 
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* opts.moduleDirectory - directory (or directories) in which to recursively look for modules. default: `"node_modules"` | 
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 | 
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* opts.preserveSymlinks - if true, doesn't resolve `basedir` to real path before resolving. | 
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This is the way Node resolves dependencies when executed with the [--preserve-symlinks](https://nodejs.org/api/all.html#cli_preserve_symlinks) flag. | 
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**Note:** this property is currently `true` by default but it will be changed to | 
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`false` in the next major version because *Node's resolution algorithm does not preserve symlinks by default*. | 
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 | 
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default `opts` values: | 
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 | 
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```js | 
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{ | 
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    paths: [], | 
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    basedir: __dirname, | 
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    extensions: ['.js'], | 
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    includeCoreModules: true, | 
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    readFile: fs.readFile, | 
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    isFile: function isFile(file, cb) { | 
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        fs.stat(file, function (err, stat) { | 
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            if (!err) { | 
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                return cb(null, stat.isFile() || stat.isFIFO()); | 
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            } | 
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            if (err.code === 'ENOENT' || err.code === 'ENOTDIR') return cb(null, false); | 
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            return cb(err); | 
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        }); | 
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    }, | 
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    isDirectory: function isDirectory(dir, cb) { | 
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        fs.stat(dir, function (err, stat) { | 
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            if (!err) { | 
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                return cb(null, stat.isDirectory()); | 
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            } | 
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            if (err.code === 'ENOENT' || err.code === 'ENOTDIR') return cb(null, false); | 
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            return cb(err); | 
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        }); | 
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    }, | 
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    realpath: function realpath(file, cb) { | 
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        var realpath = typeof fs.realpath.native === 'function' ? fs.realpath.native : fs.realpath; | 
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        realpath(file, function (realPathErr, realPath) { | 
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            if (realPathErr && realPathErr.code !== 'ENOENT') cb(realPathErr); | 
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            else cb(null, realPathErr ? file : realPath); | 
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        }); | 
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    }, | 
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    readPackage: function defaultReadPackage(readFile, pkgfile, cb) { | 
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        readFile(pkgfile, function (readFileErr, body) { | 
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            if (readFileErr) cb(readFileErr); | 
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            else { | 
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                try { | 
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                    var pkg = JSON.parse(body); | 
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                    cb(null, pkg); | 
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                } catch (jsonErr) { | 
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                    cb(null); | 
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                } | 
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            } | 
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        }); | 
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    }, | 
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    moduleDirectory: 'node_modules', | 
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    preserveSymlinks: true | 
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} | 
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``` | 
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 | 
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## resolve.sync(id, opts) | 
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Synchronously resolve the module path string `id`, returning the result and | 
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throwing an error when `id` can't be resolved. | 
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 | 
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options are: | 
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 | 
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* opts.basedir - directory to begin resolving from | 
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 | 
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* opts.extensions - array of file extensions to search in order | 
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 | 
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* opts.includeCoreModules - set to `false` to exclude node core modules (e.g. `fs`) from the search | 
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 | 
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* opts.readFileSync - how to read files synchronously | 
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 | 
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* opts.isFile - function to synchronously test whether a file exists | 
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 | 
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* opts.isDirectory - function to synchronously test whether a file exists and is a directory | 
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 | 
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* opts.realpathSync - function to synchronously resolve a potential symlink to its real path | 
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 | 
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* `opts.readPackageSync(readFileSync, pkgfile)` - function to synchronously read and parse a package.json file | 
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  * readFileSync - the passed `opts.readFileSync` or `fs.readFileSync` if not specified | 
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  * pkgfile - path to package.json | 
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 | 
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* `opts.packageFilter(pkg, dir)` - transform the parsed package.json contents before looking at the "main" field | 
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  * pkg - package data | 
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  * dir - directory that contains package.json (Note: the second argument will change to "pkgfile" in v2) | 
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 | 
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* `opts.pathFilter(pkg, path, relativePath)` - transform a path within a package | 
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  * pkg - package data | 
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  * path - the path being resolved | 
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  * relativePath - the path relative from the package.json location | 
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  * returns - a relative path that will be joined from the package.json location | 
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 | 
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* opts.paths - require.paths array to use if nothing is found on the normal `node_modules` recursive walk (probably don't use this) | 
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 | 
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  For advanced users, `paths` can also be a `opts.paths(request, start, opts)` function | 
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    * request - the import specifier being resolved | 
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    * start - lookup path | 
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    * getNodeModulesDirs - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution | 
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    * opts - the resolution options | 
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 | 
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* `opts.packageIterator(request, start, opts)` - return the list of candidate paths where the packages sources may be found (probably don't use this) | 
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    * request - the import specifier being resolved | 
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    * start - lookup path | 
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    * getPackageCandidates - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution | 
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    * opts - the resolution options | 
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 | 
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* opts.moduleDirectory - directory (or directories) in which to recursively look for modules. default: `"node_modules"` | 
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 | 
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* opts.preserveSymlinks - if true, doesn't resolve `basedir` to real path before resolving. | 
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This is the way Node resolves dependencies when executed with the [--preserve-symlinks](https://nodejs.org/api/all.html#cli_preserve_symlinks) flag. | 
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**Note:** this property is currently `true` by default but it will be changed to | 
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`false` in the next major version because *Node's resolution algorithm does not preserve symlinks by default*. | 
						|
 | 
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default `opts` values: | 
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 | 
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```js | 
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{ | 
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    paths: [], | 
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    basedir: __dirname, | 
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    extensions: ['.js'], | 
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    includeCoreModules: true, | 
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    readFileSync: fs.readFileSync, | 
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    isFile: function isFile(file) { | 
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        try { | 
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            var stat = fs.statSync(file); | 
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        } catch (e) { | 
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            if (e && (e.code === 'ENOENT' || e.code === 'ENOTDIR')) return false; | 
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            throw e; | 
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        } | 
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        return stat.isFile() || stat.isFIFO(); | 
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    }, | 
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    isDirectory: function isDirectory(dir) { | 
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        try { | 
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            var stat = fs.statSync(dir); | 
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        } catch (e) { | 
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            if (e && (e.code === 'ENOENT' || e.code === 'ENOTDIR')) return false; | 
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            throw e; | 
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        } | 
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        return stat.isDirectory(); | 
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    }, | 
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    realpathSync: function realpathSync(file) { | 
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        try { | 
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            var realpath = typeof fs.realpathSync.native === 'function' ? fs.realpathSync.native : fs.realpathSync; | 
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            return realpath(file); | 
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        } catch (realPathErr) { | 
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            if (realPathErr.code !== 'ENOENT') { | 
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                throw realPathErr; | 
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            } | 
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        } | 
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        return file; | 
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    }, | 
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    readPackageSync: function defaultReadPackageSync(readFileSync, pkgfile) { | 
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        var body = readFileSync(pkgfile); | 
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        try { | 
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            var pkg = JSON.parse(body); | 
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            return pkg; | 
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        } catch (jsonErr) {} | 
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    }, | 
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    moduleDirectory: 'node_modules', | 
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    preserveSymlinks: true | 
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} | 
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``` | 
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 | 
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# install | 
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 | 
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With [npm](https://npmjs.org) do: | 
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```sh | 
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npm install resolve | 
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``` | 
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 | 
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# license | 
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 | 
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MIT | 
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 | 
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[1]: https://npmjs.org/package/resolve | 
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[2]: https://versionbadg.es/browserify/resolve.svg | 
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[5]: https://david-dm.org/browserify/resolve.svg | 
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[6]: https://david-dm.org/browserify/resolve | 
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[7]: https://david-dm.org/browserify/resolve/dev-status.svg | 
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[8]: https://david-dm.org/browserify/resolve#info=devDependencies | 
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[11]: https://nodei.co/npm/resolve.png?downloads=true&stars=true | 
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[license-image]: https://img.shields.io/npm/l/resolve.svg | 
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[license-url]: LICENSE | 
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[downloads-image]: https://img.shields.io/npm/dm/resolve.svg | 
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[downloads-url]: https://npm-stat.com/charts.html?package=resolve | 
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[codecov-image]: https://codecov.io/gh/browserify/resolve/branch/main/graphs/badge.svg | 
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[codecov-url]: https://app.codecov.io/gh/browserify/resolve/ | 
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[actions-image]: https://img.shields.io/endpoint?url=https://github-actions-badge-u3jn4tfpocch.runkit.sh/browserify/resolve | 
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[actions-url]: https://github.com/browserify/resolve/actions
 | 
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 |