Installing

Assuming you’ve already installed Node.js, create a directory to hold your application, and make that your working directory.

Express 4.x requires Node.js 0.10 or higher.
Express 5.x requires Node.js 18 or higher.

$ mkdir myapp
$ cd myapp

Use the npm init command to create a package.json file for your application. For more information on how package.json works, see Specifics of npm’s package.json handling.

$ npm init

This command prompts you for a number of things, such as the name and version of your application. For now, you can simply hit RETURN to accept the defaults for most of them, with the following exception:

entry point: (index.js)

Enter app.js, or whatever you want the name of the main file to be. If you want it to be index.js, hit RETURN to accept the suggested default file name.

Now, install Express in the myapp directory and save it in the dependencies list. For example:

$ npm install express

To install Express temporarily and not add it to the dependencies list:

$ npm install express --no-save

By default with version npm 5.0+, `npm install` adds the module to the `dependencies` list in the `package.json` file; with earlier versions of npm, you must specify the `--save` option explicitly. Then, afterwards, running `npm install` in the app directory will automatically install modules in the dependencies list.