I wanted to use NodeJS require directive to read a JSON file inside my TypeScript application, but...
\nThe configuration.json file with the valid JSON content:
\n{\n \"api_url\": \"https://api.localhost\",\n \"api_key\": \"ZXH123\"\n}Solution
\nnpm i @types/node --save-devNodeJS, which uses CommonJS module format, offers a simple way to read JSON files via require directive; it is a synchronous operation and the file contents will be cached under require.cache object.\nTo demonstrate it, let's create a simple ConfigReader.js script which is going to load the configuration.json file as shown below:
const configuration = require('./configuration');\n\nconsole.log(configuration.api_url, configuration.api_key);After executing this script with node ConfigReader.js, we shall see the following output https://api.localhost ZXH123.\nNothing extraordinary here, yet the following things are worth noting:
require does not care about the file extension, as long as it is either .js or .json. However, if you created the configuration.js file with the following content module.exports = { api_url: 'url', api_key: 'key' }, it would be loaded before the configuration.json file.try-catch block if needed.fs core module should be used instead.Until now, we have been tinkering with NodeJS and pure JavaScript. Let's switch gears and reproduce the same functionality in TypeScript.
\nLet's create a simple file TypescriptConfigReader.ts with exactly the same content as before. We have to suffix it with .ts because TypeScript Compiler supports only the following extensions: .ts, .tsx, .d.ts.
\nConfusingly enough, we could execute this file with node TypescriptConfigReader.ts and get the same output, without any errors. There are two reasons for it:
As soon as we compile the TypescriptConfigReader.ts file with: tsc TypescriptConfigReader.ts, we will instantly see the following compilation error:
TypescriptConfigReader.ts:1:23 - error TS2580: Cannot find name 'require'. Do you need to install type definitions for node? Try `npm i @types/node`.Strangely enough, the TypescriptConfigReader.js file has also been created and it can be run without any issues via NodeJS Interpreter. So what is going on here?
\ntsc --noEmitOnError TypescriptConfigReader.ts. In this way, no JavaScript files would be emitted if any compilation errors were reported.As shown above, even one line of code can make the TypeScript Compiler unhappy. Let's move on and explore the solution space together.
\nBy shouting with the TS2580 error code, the TypeScript Compiler gave us also a decent hint on how to fix it. Let's follow its advice to some extent and install the proper Type Declarations with the following command:
\nnpm i @types/node --save-devIf you run the tsc TypescriptConfigReader.ts now, TypeScript Compiler should not complain anymore. That was simple, but before wrapping it up, let's clarify a few things:
@types/node under devDependencies. In the end, TypeScript is a development tool and TypeScript types do not exist at runtime.__dirname, __filename) or any other NodeJS built-in core modules (i.e.: fs, http), you are covered. All of them are defined under the same @types/node Type Declarations.