How to Define the Required Node.js Version in package.json?

Like the other project dependencies we can also define the node js version for a project. As we know that node is javascript runtime so it will not be contained by the normal dependencies. It ensures that the project should run and install only the compaitible node and npm version.

Approach

The define the required Node js version in the package.json file we will use the engines property. Just mention the Node js and NPM version required in the engines property.

Steps to Define Node Versions in Package.json

To define the required Node.js version in the package.json file we will have to go through few simple steps:

Step 1: Open the package.json file

Our first and foremost step should be to choose a project on which we are going to work, for example, I will be choosing a simple JavaScript project. In the project, we will be having a package.json file, if not we will have to create a package.json file in the same directory. 

Step 2: Define engines inside package.json

After creating our Package.json file we will make use of the engines field to specify the version of Node.js that the project requires in order to run, therefore we will add few lines in our Package.json file following the same syntax to specify the required Node.js version for the project:

Syntax:

"engines": {
    "node": "> or < =version_number",
    "npm": "> or < =version_number"
},

Output:

Here in the above output image, we can see that we have defined our required node version to be greater than or equal to 15.0.0 and npm version to be less than or equal to 5.0.0, therefore when we try to run any operation using node then first it will check if the required version matches with the present version or not and if not it displays errors.

Step 3: Create .npmrc

In order to display errors in the command prompt or terminal when there is a mismatch in the node.js version, we will have to create a .npmrc file in the same directory in which the package.json is present.

What is the .npmrc file? 

In simple terms .npmrc file can be defined as a file that is a configuration file for NPM, and it defines the settings on how NPM should behave when running commands.

Now create a .npmrc file and add the following code engine-strict=true in it, because of which it will force display errors if there is a mismatch in the versions of node and npm.

Step 4: Run Installation command

Now, our final step should be to test if we are getting errors or not while there is a Node.js and npm version mismatch, and to test it I will be using a simple command npm install and we get the following errors. 

Output:

Reference: How to create a Package.json file: https://www.geeksforgeeks.org/node-js-package-json/