isMain(importMetaUrl, cjsModule, mainModule)

Determines if the current module is being executed as the main script.

Parameters

Returns

• true → If the module is the main entry point.
• false → If the module is imported or parameters are invalid.

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.

Example

          
            1const { isMain } = require("./mainCheck");3if (isMain(null, module, require.main)) {4  console.log("This module is running directly!");5}
          
        

Edge Cases

• Works for both ES modules and CommonJS.
• Returns false when the module is imported.
• Handles invalid inputs gracefully.
• In ESM, require is unavailable, so CommonJS checks are skipped.

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