Something I've needed for a side project is the ability to retrieve what version of a dependency has currently been resolved. It was quite hard to search around this online so I'm writing how to do it for future folks searching for this.

The below examples are based on this example project on GitLab.com.

Let's say that we loosely pin typescript, but at runtime want to log out what version the following resolves to:

{
  "devDependencies": {
    "typescript": "^4.x"
  }
}

Fortunately all NPM packages get distributed with their package.jsons intact, so we can require/import the file and then log it out.

Node.JS

With Node.JS this is trivial, as we can simply require the file, and then interact with it as an object:

const packageJson = require('typescript/package.json');

console.log(`Currently running TypeScript v${packageJson.version}`);

When we run it:

node index.js
# Outputs:
# Currently running Typescript v4.9.5

TypeScript

TypeScript requires a slightly more complex setup, as we need to specify the resolveJsonModule compiler option, which means we have a tsconfig.json similar to:

{
  "$schema": "https://json.schemastore.org/tsconfig",
  "compilerOptions": {
    "resolveJsonModule": true
  }
}

Then, we can write the following code:

import * as packageJson from 'typescript/package.json';

console.log(`Currently running Typescript v${packageJson.version}`);

Therefore, we can run:

npm run build
node dist/index.js
# Outputs:
# Currently running Typescript v4.9.5