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 ## resolve(id, opts={}, cb)
48 Asynchronously resolve the module path string `id` into `cb(err, res [, pkg])`, where `pkg` (if defined) is the data from `package.json`.
52 * opts.basedir - directory to begin resolving from
54 * opts.package - `package.json` data applicable to the module being loaded
56 * opts.extensions - array of file extensions to search in order
58 * opts.readFile - how to read files asynchronously
60 * opts.isFile - function to asynchronously test whether a file exists
62 * opts.isDirectory - function to asynchronously test whether a directory exists
64 * opts.realpath - function to asynchronously resolve a potential symlink to its real path
66 * `opts.packageFilter(pkg, pkgfile, dir)` - transform the parsed package.json contents before looking at the "main" field
68 * pkgfile - path to package.json
69 * dir - directory for package.json
71 * `opts.pathFilter(pkg, path, relativePath)` - transform a path within a package
73 * path - the path being resolved
74 * relativePath - the path relative from the package.json location
75 * returns - a relative path that will be joined from the package.json location
77 * opts.paths - require.paths array to use if nothing is found on the normal `node_modules` recursive walk (probably don't use this)
79 For advanced users, `paths` can also be a `opts.paths(request, start, opts)` function
80 * request - the import specifier being resolved
82 * getNodeModulesDirs - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution
83 * opts - the resolution options
85 * `opts.packageIterator(request, start, opts)` - return the list of candidate paths where the packages sources may be found (probably don't use this)
86 * request - the import specifier being resolved
88 * getPackageCandidates - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution
89 * opts - the resolution options
91 * opts.moduleDirectory - directory (or directories) in which to recursively look for modules. default: `"node_modules"`
93 * opts.preserveSymlinks - if true, doesn't resolve `basedir` to real path before resolving.
94 This is the way Node resolves dependencies when executed with the [--preserve-symlinks](https://nodejs.org/api/all.html#cli_preserve_symlinks) flag.
95 **Note:** this property is currently `true` by default but it will be changed to
96 `false` in the next major version because *Node's resolution algorithm does not preserve symlinks by default*.
98 default `opts` values:
105 readFile: fs.readFile,
106 isFile: function isFile(file, cb) {
107 fs.stat(file, function (err, stat) {
109 return cb(null, stat.isFile() || stat.isFIFO());
111 if (err.code === 'ENOENT' || err.code === 'ENOTDIR') return cb(null, false);
115 isDirectory: function isDirectory(dir, cb) {
116 fs.stat(dir, function (err, stat) {
118 return cb(null, stat.isDirectory());
120 if (err.code === 'ENOENT' || err.code === 'ENOTDIR') return cb(null, false);
124 realpath: function realpath(file, cb) {
125 var realpath = typeof fs.realpath.native === 'function' ? fs.realpath.native : fs.realpath;
126 realpath(file, function (realPathErr, realPath) {
127 if (realPathErr && realPathErr.code !== 'ENOENT') cb(realPathErr);
128 else cb(null, realPathErr ? file : realPath);
131 moduleDirectory: 'node_modules',
132 preserveSymlinks: true
136 ## resolve.sync(id, opts)
138 Synchronously resolve the module path string `id`, returning the result and
139 throwing an error when `id` can't be resolved.
143 * opts.basedir - directory to begin resolving from
145 * opts.extensions - array of file extensions to search in order
147 * opts.readFile - how to read files synchronously
149 * opts.isFile - function to synchronously test whether a file exists
151 * opts.isDirectory - function to synchronously test whether a directory exists
153 * opts.realpathSync - function to synchronously resolve a potential symlink to its real path
155 * `opts.packageFilter(pkg, dir)` - transform the parsed package.json contents before looking at the "main" field
157 * dir - directory for package.json (Note: the second argument will change to "pkgfile" in v2)
159 * `opts.pathFilter(pkg, path, relativePath)` - transform a path within a package
161 * path - the path being resolved
162 * relativePath - the path relative from the package.json location
163 * returns - a relative path that will be joined from the package.json location
165 * opts.paths - require.paths array to use if nothing is found on the normal `node_modules` recursive walk (probably don't use this)
167 For advanced users, `paths` can also be a `opts.paths(request, start, opts)` function
168 * request - the import specifier being resolved
169 * start - lookup path
170 * getNodeModulesDirs - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution
171 * opts - the resolution options
173 * `opts.packageIterator(request, start, opts)` - return the list of candidate paths where the packages sources may be found (probably don't use this)
174 * request - the import specifier being resolved
175 * start - lookup path
176 * getPackageCandidates - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution
177 * opts - the resolution options
179 * opts.moduleDirectory - directory (or directories) in which to recursively look for modules. default: `"node_modules"`
181 * opts.preserveSymlinks - if true, doesn't resolve `basedir` to real path before resolving.
182 This is the way Node resolves dependencies when executed with the [--preserve-symlinks](https://nodejs.org/api/all.html#cli_preserve_symlinks) flag.
183 **Note:** this property is currently `true` by default but it will be changed to
184 `false` in the next major version because *Node's resolution algorithm does not preserve symlinks by default*.
186 default `opts` values:
193 readFileSync: fs.readFileSync,
194 isFile: function isFile(file) {
196 var stat = fs.statSync(file);
198 if (e && (e.code === 'ENOENT' || e.code === 'ENOTDIR')) return false;
201 return stat.isFile() || stat.isFIFO();
203 isDirectory: function isDirectory(dir) {
205 var stat = fs.statSync(dir);
207 if (e && (e.code === 'ENOENT' || e.code === 'ENOTDIR')) return false;
210 return stat.isDirectory();
212 realpathSync: function realpathSync(file) {
214 var realpath = typeof fs.realpathSync.native === 'function' ? fs.realpathSync.native : fs.realpathSync;
215 return realpath(file);
216 } catch (realPathErr) {
217 if (realPathErr.code !== 'ENOENT') {
223 moduleDirectory: 'node_modules',
224 preserveSymlinks: true
228 ## resolve.isCore(pkg)
230 Return whether a package is in core.
234 With [npm](https://npmjs.org) do: