Detect if Running in TS Node

1.0.5 · active · verified Sun Apr 19

The `detect-ts-node` package is a utility designed to programmatically determine if the currently executing JavaScript or TypeScript code is running within a `ts-node` environment. It provides a single boolean export that is `true` when `ts-node` is active and `false` otherwise. The current stable version is 1.0.5. Given its highly focused and stable nature, the package likely maintains a very low release cadence, with updates primarily addressing internal `ts-node` changes or minor bug fixes. A key differentiator is its simplicity and direct implementation, based on established discussions within the `ts-node` community, making it a reliable choice for developers who need to implement conditional logic, configuration adjustments, or specific debugging behaviors when operating under `ts-node` versus a pre-compiled JavaScript environment. It explicitly targets `ts-node` detection, distinguishing it from broader TypeScript compilation environment checks.

Common errors

```
TypeError: (0, _detectTsNode.default) is not a function
```
cause Attempting to call `detectTSNode` as a function when it is a boolean value, or incorrect CommonJS interop with ESM default exports.

fix Ensure you are treating `detectTSNode` as a boolean (`if (detectTSNode) { ... }`) and not invoking it. For CommonJS, use `const detectTSNode = require('detect-ts-node');` directly without `.default` if you encounter this.
```
SyntaxError: Named export 'detectTSNode' not found. Did you mean 'default'?
```
cause Attempting to import the default export using named import syntax in an ESM module.

fix Change `import { detectTSNode } from 'detect-ts-node';` to `import detectTSNode from 'detect-ts-node';` to correctly import the default export.

Warnings

gotcha The detection mechanism relies on internal heuristics that `ts-node` exposes. While generally robust, future major versions of `ts-node` could theoretically change these internals, potentially leading to incorrect detection in `detect-ts-node` without a corresponding package update.
Fix: Always test `detect-ts-node` against new major `ts-node` versions if its accuracy is critical to your application's conditional logic. Monitor the `detect-ts-node` GitHub repository for updates addressing `ts-node` changes.
gotcha This package is specifically designed to detect `ts-node`. It does not detect other TypeScript compilation environments such as `ts-jest`, `ts-loader` for Webpack, `esbuild` with TypeScript, or direct `tsc` compilation. Its scope is limited to `ts-node`.
Fix: If you need to detect broader TypeScript compilation contexts, implement custom checks based on specific environment variables (e.g., `TS_JEST` for Jest) or specific build tool flags that indicate their presence.

Install

npm install detect-ts-node npm
yarn add detect-ts-node yarn
pnpm add detect-ts-node pnpm

Imports

detectTSNode
wrong:
```
import { detectTSNode } from 'detect-ts-node';
```
correct:
```
import detectTSNode from 'detect-ts-node';
```
The package exports a single boolean value as its default export. Attempting to use named import syntax for `detectTSNode` will result in a runtime error or a build error.
detectTSNode
wrong:
```
const detectTSNode = require('detect-ts-node').default;
```
correct:
```
const detectTSNode = require('detect-ts-node');
```
In CommonJS environments, `require('detect-ts-node')` directly resolves to the default export. Explicitly accessing `.default` is unnecessary and can be incorrect if the environment does not correctly interop ESM default exports.
type of detectTSNode
```
// No specific type import is needed, as `detectTSNode` is a boolean value.
// TypeScript's type inference handles it automatically.
```
While the package ships TypeScript types, `detectTSNode` itself is a simple boolean (`boolean` type). No dedicated type import is required or available for this value.

Quickstart

Demonstrates how to import and use the `detectTSNode` boolean value to conditionally execute logic or set configurations based on whether the code is running within a `ts-node` environment.

import detectTSNode from "detect-ts-node";

function initializeApplication() {
  if (detectTSNode) {
    console.log("TS Node detected. Applying development-specific configurations.");
    // Example: Dynamically load '.env.development' or enable hot-reloading
    process.env.NODE_ENV = 'development';
    // Potentially load a different config module
    // const config = require('./config.ts-node').default;
  } else {
    console.log("Not running in TS Node. Standard production or compiled JS environment.");
    // Example: Load '.env.production' or rely on pre-compiled assets
    process.env.NODE_ENV = 'production';
    // const config = require('./config.js').default;
  }
  console.log(`Application environment set to: ${process.env.NODE_ENV}`);
}

initializeApplication();

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