How to import package.json in TypeScript?

Question

I'm trying to import my package.json file in TypeScript and it doesn't seem to work. Specifically, I'm just trying to import it so that I can access the name and version properties for a log statement. Something like:

import * as pjson from '../package.json'; // other code here log.info(`${pjson.name}:${pjson.version}` started on port ...); 

We have this same syntax elsewhere in other projects that use Node/Babel, but I'm trying to introduce some TypeScript around these parts. Elsewhere we'd do something like:

import { name, version} from '../package.json'; 

That doesn't work here however. I followed the instructions at https://www.npmjs.com/package/json-d-ts which at least made the error on my import statement go away, but now when I try to access properties I get the following error:

src/index.ts(20,21): error TS2339: Property 'name' does not exist on type 'typeof import("*.json")'. src/index.ts(20,35): error TS2339: Property 'version' does not exist on type 'typeof import("*.json")'. 

Is there a way to fix this, or do I just have to hardcode these values somewhere (rather than dynamically retrieving them from package.json)? Maybe I can declare a type for import("*.json") somehow with these properties defined on it?

Answer 1

How to import *.json ?

As already answered you need Typescript >= 2.9 and the following settings in tsconfig.json:

{   "resolveJsonModule": true,   "esModuleInterop": true,   "module": "commonjs" } 

But there are restrictions:

• You must compile to CommonJS
• All your imported JSONs must reside under the "rootDir"

Unfortunately the "rootDir" is very often a folder beneath package.json like './src' and things would fail.

So:
How to import package.json ? You can require it:
const pjson = require('../package.json');

If you use npm.start: you don't need to :

The package.json fields are tacked onto the npm_package_ prefix. So, for instance, if you had {"name":"foo", "version":"1.2.5"} in your package.json file, then your package scripts would have the npm_package_name environment variable set to “foo”, and the npm_package_version set to “1.2.5”. You can access these variables in your code with process.env.npm_package_name and process.env.npm_package_version, and so on for other fields.