Behavior

1. CommonJS Detection:

             
               1if (typeof mainModule !== "undefined" && cjsModule === mainModule) {2    return require.main === mainModule;3}
             
           

   Checks if the current module is the main script.

2. ES Module Detection:

             
               1const filename = fileURLToPath(importMetaUrl);2return filename === process.argv[1];
             
           

   Converts import.meta.url to a path and compares with the Node.js entry file.

3. Safe Fallback: Returns false for unknown or invalid inputs.