Cannot be compiled under 'isolatedModules' because it is considered a global script file

# Cannot be compiled under '--isolatedModules' because it is considered a global

The error "Cannot be compiled under '--isolatedModules' because it is considered a global script file" occurs when we have a file in our project that doesn't contain an import or export statement.

To solve the error, add an export {} line to the file to make it an ES module.

Here is an example of how the error occurs.

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// ⛔️ Error: All files must be modules when
// the '--isolatedModules' flag is provided.
// 'index.ts' cannot be compiled under
// '--isolatedModules' because it is considered
// a global script file. Add an import, export,
// or an empty 'export {}' statement to make it a module.ts(1208)
const country = 'Austria';

The index.ts file doesn't contain any import or export statements, so it is not considered an ES Module by TypeScript.

# Add an import or export statement to the module

To solve the error, add an import or export statement to the module.

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const country = 'Austria';

export {}; // 👈️ if you don't have anything else to export

We used the export {} line in our index.ts file to mark it as a module. A module is a file that contains at least 1 import or export statement.

# Make sure you don't have an empty .ts file in your project

Make sure that you don't have an empty .ts file somewhere in your project, and if you do, either remove the file or add an export {} line to make it an ES module.

Empty files are treated like legacy scripts, which is not allowed with isolatedModules enabled.

# Set isolatedModules to false in tsconfig.json

If this doesn't get the error resolved, try setting isolatedModules to false in your tsconfig.json file.

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{
  "compilerOptions": {
    "isolatedModules": false,
    // ... rest
  }
}

When the isolatedModules option is set to true, all files in your project must be modules (must contain at least 1 import or export statement).

I've also written a detailed guide on how to import values from another file in TS.

# Importing and re-exporting types

Another thing that may cause an error with isolatedModules set to true is if you are importing a type and then re-exporting it.

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import { EmployeeType } from './another-file';

// ⛔️ Error: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.ts(1205)
export { EmployeeType };

Because of how transpilers work, the setting wants us to explicitly use the export type syntax.

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import { EmployeeType } from './another-file';

export type { EmployeeType };

The export type syntax guarantees that the export statement will be removed from your code during compilation and it won't end up causing a runtime error because you are trying to export something that doesn't exist (types get removed during compilation).