3 implements the [node `require.resolve()`
4 algorithm](https://nodejs.org/api/modules.html#modules_all_together)
5 such that you can `require.resolve()` on behalf of a file asynchronously and
8 [![build status](https://secure.travis-ci.org/browserify/resolve.png)](http://travis-ci.org/browserify/resolve)
12 asynchronously resolve:
15 var resolve = require('resolve');
16 resolve('tap', { basedir: __dirname }, function (err, res) {
17 if (err) console.error(err);
18 else console.log(res);
23 $ node example/async.js
24 /home/substack/projects/node-resolve/node_modules/tap/lib/main.js
27 synchronously resolve:
30 var resolve = require('resolve');
31 var res = resolve.sync('tap', { basedir: __dirname });
36 $ node example/sync.js
37 /home/substack/projects/node-resolve/node_modules/tap/lib/main.js
43 var resolve = require('resolve');
46 For both the synchronous and asynchronous methods, errors may have any of the following `err.code` values:
48 - `MODULE_NOT_FOUND`: the given path string (`id`) could not be resolved to a module
49 - `INVALID_BASEDIR`: the specified `opts.basedir` doesn't exist, or is not a directory
50 - `INVALID_PACKAGE_MAIN`: a `package.json` was encountered with an invalid `main` property (eg. not a string)
52 ## resolve(id, opts={}, cb)
54 Asynchronously resolve the module path string `id` into `cb(err, res [, pkg])`, where `pkg` (if defined) is the data from `package.json`.
58 * opts.basedir - directory to begin resolving from
60 * opts.package - `package.json` data applicable to the module being loaded
62 * opts.extensions - array of file extensions to search in order
64 * opts.includeCoreModules - set to `false` to exclude node core modules (e.g. `fs`) from the search
66 * opts.readFile - how to read files asynchronously
68 * opts.isFile - function to asynchronously test whether a file exists
70 * opts.isDirectory - function to asynchronously test whether a directory exists
72 * opts.realpath - function to asynchronously resolve a potential symlink to its real path
74 * `opts.packageFilter(pkg, pkgfile, dir)` - transform the parsed package.json contents before looking at the "main" field
76 * pkgfile - path to package.json
77 * dir - directory for package.json
79 * `opts.pathFilter(pkg, path, relativePath)` - transform a path within a package
81 * path - the path being resolved
82 * relativePath - the path relative from the package.json location
83 * returns - a relative path that will be joined from the package.json location
85 * opts.paths - require.paths array to use if nothing is found on the normal `node_modules` recursive walk (probably don't use this)
87 For advanced users, `paths` can also be a `opts.paths(request, start, opts)` function
88 * request - the import specifier being resolved
90 * getNodeModulesDirs - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution
91 * opts - the resolution options
93 * `opts.packageIterator(request, start, opts)` - return the list of candidate paths where the packages sources may be found (probably don't use this)
94 * request - the import specifier being resolved
96 * getPackageCandidates - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution
97 * opts - the resolution options
99 * opts.moduleDirectory - directory (or directories) in which to recursively look for modules. default: `"node_modules"`
101 * opts.preserveSymlinks - if true, doesn't resolve `basedir` to real path before resolving.
102 This is the way Node resolves dependencies when executed with the [--preserve-symlinks](https://nodejs.org/api/all.html#cli_preserve_symlinks) flag.
103 **Note:** this property is currently `true` by default but it will be changed to
104 `false` in the next major version because *Node's resolution algorithm does not preserve symlinks by default*.
106 default `opts` values:
113 includeCoreModules: true,
114 readFile: fs.readFile,
115 isFile: function isFile(file, cb) {
116 fs.stat(file, function (err, stat) {
118 return cb(null, stat.isFile() || stat.isFIFO());
120 if (err.code === 'ENOENT' || err.code === 'ENOTDIR') return cb(null, false);
124 isDirectory: function isDirectory(dir, cb) {
125 fs.stat(dir, function (err, stat) {
127 return cb(null, stat.isDirectory());
129 if (err.code === 'ENOENT' || err.code === 'ENOTDIR') return cb(null, false);
133 realpath: function realpath(file, cb) {
134 var realpath = typeof fs.realpath.native === 'function' ? fs.realpath.native : fs.realpath;
135 realpath(file, function (realPathErr, realPath) {
136 if (realPathErr && realPathErr.code !== 'ENOENT') cb(realPathErr);
137 else cb(null, realPathErr ? file : realPath);
140 moduleDirectory: 'node_modules',
141 preserveSymlinks: true
145 ## resolve.sync(id, opts)
147 Synchronously resolve the module path string `id`, returning the result and
148 throwing an error when `id` can't be resolved.
152 * opts.basedir - directory to begin resolving from
154 * opts.extensions - array of file extensions to search in order
156 * opts.includeCoreModules - set to `false` to exclude node core modules (e.g. `fs`) from the search
158 * opts.readFile - how to read files synchronously
160 * opts.isFile - function to synchronously test whether a file exists
162 * opts.isDirectory - function to synchronously test whether a directory exists
164 * opts.realpathSync - function to synchronously resolve a potential symlink to its real path
166 * `opts.packageFilter(pkg, dir)` - transform the parsed package.json contents before looking at the "main" field
168 * dir - directory for package.json (Note: the second argument will change to "pkgfile" in v2)
170 * `opts.pathFilter(pkg, path, relativePath)` - transform a path within a package
172 * path - the path being resolved
173 * relativePath - the path relative from the package.json location
174 * returns - a relative path that will be joined from the package.json location
176 * opts.paths - require.paths array to use if nothing is found on the normal `node_modules` recursive walk (probably don't use this)
178 For advanced users, `paths` can also be a `opts.paths(request, start, opts)` function
179 * request - the import specifier being resolved
180 * start - lookup path
181 * getNodeModulesDirs - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution
182 * opts - the resolution options
184 * `opts.packageIterator(request, start, opts)` - return the list of candidate paths where the packages sources may be found (probably don't use this)
185 * request - the import specifier being resolved
186 * start - lookup path
187 * getPackageCandidates - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution
188 * opts - the resolution options
190 * opts.moduleDirectory - directory (or directories) in which to recursively look for modules. default: `"node_modules"`
192 * opts.preserveSymlinks - if true, doesn't resolve `basedir` to real path before resolving.
193 This is the way Node resolves dependencies when executed with the [--preserve-symlinks](https://nodejs.org/api/all.html#cli_preserve_symlinks) flag.
194 **Note:** this property is currently `true` by default but it will be changed to
195 `false` in the next major version because *Node's resolution algorithm does not preserve symlinks by default*.
197 default `opts` values:
204 includeCoreModules: true,
205 readFileSync: fs.readFileSync,
206 isFile: function isFile(file) {
208 var stat = fs.statSync(file);
210 if (e && (e.code === 'ENOENT' || e.code === 'ENOTDIR')) return false;
213 return stat.isFile() || stat.isFIFO();
215 isDirectory: function isDirectory(dir) {
217 var stat = fs.statSync(dir);
219 if (e && (e.code === 'ENOENT' || e.code === 'ENOTDIR')) return false;
222 return stat.isDirectory();
224 realpathSync: function realpathSync(file) {
226 var realpath = typeof fs.realpathSync.native === 'function' ? fs.realpathSync.native : fs.realpathSync;
227 return realpath(file);
228 } catch (realPathErr) {
229 if (realPathErr.code !== 'ENOENT') {
235 moduleDirectory: 'node_modules',
236 preserveSymlinks: true
242 With [npm](https://npmjs.org) do: