1# resolve 2 3implements the [node `require.resolve()` 4algorithm](https://nodejs.org/api/modules.html#modules_all_together) 5such that you can `require.resolve()` on behalf of a file asynchronously and 6synchronously 7 8[![build status](https://secure.travis-ci.org/browserify/resolve.png)](http://travis-ci.org/browserify/resolve) 9 10# example 11 12asynchronously resolve: 13 14```js 15var resolve = require('resolve'); 16resolve('tap', { basedir: __dirname }, function (err, res) { 17 if (err) console.error(err); 18 else console.log(res); 19}); 20``` 21 22``` 23$ node example/async.js 24/home/substack/projects/node-resolve/node_modules/tap/lib/main.js 25``` 26 27synchronously resolve: 28 29```js 30var resolve = require('resolve'); 31var res = resolve.sync('tap', { basedir: __dirname }); 32console.log(res); 33``` 34 35``` 36$ node example/sync.js 37/home/substack/projects/node-resolve/node_modules/tap/lib/main.js 38``` 39 40# methods 41 42```js 43var resolve = require('resolve'); 44``` 45 46For both the synchronous and asynchronous methods, errors may have any of the following `err.code` values: 47 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) 51 52## resolve(id, opts={}, cb) 53 54Asynchronously resolve the module path string `id` into `cb(err, res [, pkg])`, where `pkg` (if defined) is the data from `package.json`. 55 56options are: 57 58* opts.basedir - directory to begin resolving from 59 60* opts.package - `package.json` data applicable to the module being loaded 61 62* opts.extensions - array of file extensions to search in order 63 64* opts.includeCoreModules - set to `false` to exclude node core modules (e.g. `fs`) from the search 65 66* opts.readFile - how to read files asynchronously 67 68* opts.isFile - function to asynchronously test whether a file exists 69 70* opts.isDirectory - function to asynchronously test whether a directory exists 71 72* opts.realpath - function to asynchronously resolve a potential symlink to its real path 73 74* `opts.packageFilter(pkg, pkgfile, dir)` - transform the parsed package.json contents before looking at the "main" field 75 * pkg - package data 76 * pkgfile - path to package.json 77 * dir - directory for package.json 78 79* `opts.pathFilter(pkg, path, relativePath)` - transform a path within a package 80 * pkg - package data 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 84 85* opts.paths - require.paths array to use if nothing is found on the normal `node_modules` recursive walk (probably don't use this) 86 87 For advanced users, `paths` can also be a `opts.paths(request, start, opts)` function 88 * request - the import specifier being resolved 89 * start - lookup path 90 * getNodeModulesDirs - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution 91 * opts - the resolution options 92 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 95 * start - lookup path 96 * getPackageCandidates - a thunk (no-argument function) that returns the paths using standard `node_modules` resolution 97 * opts - the resolution options 98 99* opts.moduleDirectory - directory (or directories) in which to recursively look for modules. default: `"node_modules"` 100 101* opts.preserveSymlinks - if true, doesn't resolve `basedir` to real path before resolving. 102This 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*. 105 106default `opts` values: 107 108```js 109{ 110 paths: [], 111 basedir: __dirname, 112 extensions: ['.js'], 113 includeCoreModules: true, 114 readFile: fs.readFile, 115 isFile: function isFile(file, cb) { 116 fs.stat(file, function (err, stat) { 117 if (!err) { 118 return cb(null, stat.isFile() || stat.isFIFO()); 119 } 120 if (err.code === 'ENOENT' || err.code === 'ENOTDIR') return cb(null, false); 121 return cb(err); 122 }); 123 }, 124 isDirectory: function isDirectory(dir, cb) { 125 fs.stat(dir, function (err, stat) { 126 if (!err) { 127 return cb(null, stat.isDirectory()); 128 } 129 if (err.code === 'ENOENT' || err.code === 'ENOTDIR') return cb(null, false); 130 return cb(err); 131 }); 132 }, 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); 138 }); 139 }, 140 moduleDirectory: 'node_modules', 141 preserveSymlinks: true 142} 143``` 144 145## resolve.sync(id, opts) 146 147Synchronously resolve the module path string `id`, returning the result and 148throwing an error when `id` can't be resolved. 149 150options are: 151 152* opts.basedir - directory to begin resolving from 153 154* opts.extensions - array of file extensions to search in order 155 156* opts.includeCoreModules - set to `false` to exclude node core modules (e.g. `fs`) from the search 157 158* opts.readFile - how to read files synchronously 159 160* opts.isFile - function to synchronously test whether a file exists 161 162* opts.isDirectory - function to synchronously test whether a directory exists 163 164* opts.realpathSync - function to synchronously resolve a potential symlink to its real path 165 166* `opts.packageFilter(pkg, dir)` - transform the parsed package.json contents before looking at the "main" field 167 * pkg - package data 168 * dir - directory for package.json (Note: the second argument will change to "pkgfile" in v2) 169 170* `opts.pathFilter(pkg, path, relativePath)` - transform a path within a package 171 * pkg - package data 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 175 176* opts.paths - require.paths array to use if nothing is found on the normal `node_modules` recursive walk (probably don't use this) 177 178 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 183 184* `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 189 190* opts.moduleDirectory - directory (or directories) in which to recursively look for modules. default: `"node_modules"` 191 192* opts.preserveSymlinks - if true, doesn't resolve `basedir` to real path before resolving. 193This 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*. 196 197default `opts` values: 198 199```js 200{ 201 paths: [], 202 basedir: __dirname, 203 extensions: ['.js'], 204 includeCoreModules: true, 205 readFileSync: fs.readFileSync, 206 isFile: function isFile(file) { 207 try { 208 var stat = fs.statSync(file); 209 } catch (e) { 210 if (e && (e.code === 'ENOENT' || e.code === 'ENOTDIR')) return false; 211 throw e; 212 } 213 return stat.isFile() || stat.isFIFO(); 214 }, 215 isDirectory: function isDirectory(dir) { 216 try { 217 var stat = fs.statSync(dir); 218 } catch (e) { 219 if (e && (e.code === 'ENOENT' || e.code === 'ENOTDIR')) return false; 220 throw e; 221 } 222 return stat.isDirectory(); 223 }, 224 realpathSync: function realpathSync(file) { 225 try { 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') { 230 throw realPathErr; 231 } 232 } 233 return file; 234 }, 235 moduleDirectory: 'node_modules', 236 preserveSymlinks: true 237} 238``` 239 240# install 241 242With [npm](https://npmjs.org) do: 243 244```sh 245npm install resolve 246``` 247 248# license 249 250MIT 251