Installing

First, create a directory to hold your application, if you haven’t already done so, and make that your working directory.

$ mkdir myapp
$ cd myapp

Create a package.json file in the directory of interest, if it does not exist already, with the npm init command.

$ npm init

Install Express in the app directory and save it in the dependencies list:

$ npm install express --save

To install Express temporarily, and not add it to the dependencies list, omit the --save option:

$ npm install express