In node.JS how can I get the path of a module I have loaded via require that is *not* mine (i.e. in some node_module)

Solution 1:

If I correctly understand your question, you should use require.resolve():

Use the internal require() machinery to look up the location of a module, but rather than loading the module, just return the resolved filename.

Example: var pathToModule = require.resolve('module');

Solution 2:

require.resolve() is a partial answer. The accepted answer may work for many node modules, but won't work for all of them.

require.resolve("moduleName") doesn't give you the directory where the module is installed; it gives you the location of the file defined in the main attribute in the module's package.json.

That might be moduleName/index.js or it could be moduleName/lib/moduleName.js. In the latter case, path.dirname(require.resolve("moduleName")) will return a directory you may not want or expect: node_modules/moduleName/lib

The correct way to get the complete path to a specific module is by resolving the filename:

let readmePath = require.resolve("moduleName/README.md");

If you just want the directory for the module (maybe you're going to make a lot of path.join() calls), then resolve the package.json — which must always be in the root of the project — and pass to path.dirname():

let packagePath = path.dirname(require.resolve("moduleName/package.json"));

Solution 3:

FYI, require.resolve returns the module identifier according to CommonJS. In node.js this is the filename. In webpack this is a number.

In webpack situation, here is my solution to find out the module path:

const pathToModule = require.resolve('module/to/require');
console.log('pathToModule is', pathToModule); // a number, eg. 8
console.log('__webpack_modules__[pathToModule] is', __webpack_modules__[pathToModule]);

Then from __webpack_modules__[pathToModule] I got information like this:

(function(module, exports, __webpack_require__) {

    eval("module.exports = (__webpack_require__(6))(85);\n\n//////////////////\n// 
    WEBPACK FOOTER\n// delegated ./node_modules/echarts/lib/echarts.js from dll-reference vendor_da75d351571a5de37e2e\n// module id = 8\n// module chunks = 0\n\n//# sourceURL=webpack:///delegated_./node_modules/echarts/lib/echarts.js_from_dll-reference_vendor_da75d351571a5de37e2e?");

    /***/
})

Turned out I required old scripts from previous dll build file(for faster build speed), so that my updated module file didn't work as I expected. Finally I rebuilt my dll file and solved my problem.

Ref: Using require.resolve to get resolved file path (node)

Solution 4:

I hope I correctly understand your needs: to get entry point file of some module. Let's say you want to get entry point of jugglingdb module:

node
> require('module')._resolveFilename('jugglingdb')
'/usr/local/lib/node_modules/jugglingdb/index.js'

As you can see this is not "official" way to get this kind of information about module, so behavior of this function may change from version to version. I've found it in node source: https://github.com/joyent/node/blob/master/lib/module.js#L280