x-ray x-ray - 29 days ago 17
Javascript Question

Node.js: Get (absolute) root path of installed npm package

Task



I'm looking for an universal way to get the (absolute) root path of an installed npm package in Node.js.

Problem



I know about
require.resolve
, but that will give me the entry point (path to the main module) rather than the root path of the package.

Take
bootstrap-sass
as an example. Say it's installed locally in a project folder
C:\dev\my-project
. Then what I'm looking for is
C:\dev\my-project\node_modules\bootstrap-sass
.
require.resolve('bootstrap-sass')
will return
C:\dev\my-project\node_modules\bootstrap-sass\assets\javascripts\bootstrap.js
.

I can think of several methods how to get the package's root path:

Solution #1



var packageRoot = path.resolve('node_modules/bootstrap-sass');
console.log(packageRoot);


This will work fine for packages installed locally in
node_modules
folder. However, if I'm in a subfolder, I need to resolve
../node_modules/bootstrap-sass
, and it get's more complicated with more nested folders. In addition, this does not work for globally installed modules.

Solution #2



var packageRoot = require.resolve('bootstrap-sass')
.match(/^.*[\/\\]node_modules[\/\\][^\/\\]*/)[0];
console.log(packageRoot);


This will work for local and global modules installed in
node_modules
folder. The regex will match everything up to the last
node_modules
path element plus the following path element. However this will fail if a package's entry point is set to another package (e.g.
"main": "./node_modules/sub-package"
in
package.json
).

Solution #3



var escapeStringRegexp = require('escape-string-regexp');

/**
* Get the root path of a npm package installed in node_modules.
* @param {string} packageName The name of the package.
* @returns {string} Root path of the package without trailing slash.
* @throws Will throw an error if the package root path cannot be resolved
*/
function packageRootPath(packageName) {
var mainModulePath = require.resolve(packageName);
var escapedPackageName = escapeStringRegexp(packageName);
var regexpStr = '^.*[\\/\\\\]node_modules[\\/\\\\]' + escapedPackageName +
'(?=[\\/\\\\])';
var rootPath = mainModulePath.match(regexpStr);
if (rootPath) {
return rootPath[0];
} else {
var msg = 'Could not resolve package root path for package `' +
packageName + '`.'
throw new Error(msg);
}
}

var packageRoot = packageRootPath('bootstrap-sass');
console.log(packageRoot);


This function should work for all packages installed in a
node_modules
folder.

But...



I wonder if this rather simple task cannot be solved in a simpler and less hacky way. To me it looks like something that should already be built into Node.js. Any suggestions?

Answer

Try this:

require.resolve('bootstrap-sass/package.json')

which returns:

path_to_my_project/node_modules/bootstrap-sass/package.json 

You can now get rid of 'package.json' path suffix such as:

var path = require('path') // npm install path
var bootstrapPath = path.dirname(require.resolve('bootstrap-sass/package.json'))

Since it is mandatory for every package to contain package.json file, this should always work (see What is a package?).