Using npm packages in your projects

Once you have installed a package in node_modules, you can use it in your code.

Using unscoped packages in your projects

Node.js module

If you are creating a Node.js module, you can use a package in your module by passing it as an argument to the require function.

Example: using lodash in a Node.js module

For example, to use the lodash package in a Node.js module, in the root directory of the module, create a file named index.js with the following contents:

// index.js
var lodash = require('lodash');

var output = lodash.without([1, 2, 3], 1);
console.log(output);

Run the code using node index.js. It should output [2, 3].

package.json file

In package.json, list the package under dependencies. You can optionally include a semantic version.

{
  "dependencies": {
    "@package_name": "^1.0.0"
  }
}

Using scoped packages in your projects

To use a scoped package, simply include the scope wherever you use the package name.

Node.js module

When requiring a scoped package in the index.js file of your Node.js module, you must reference the scope in addition to the package name:

var projectName = require("@scope/package-name")

package.json file

In package.json:

{
  "dependencies": {
    "@scope/package_name": "^1.0.0"
  }
}

Resolving “Cannot find module” errors

If you have not properly installed a package, you will receive an error when you try to use it in your code. For example, if you reference the lodash package without installing it, you would see the following error:

module.js:340
    throw err;
          ^
Error: Cannot find module 'lodash'

To resolve “cannot find module” errors, run the appropriate install command in the same directory as your project’s index.js file:


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