ts-node running .ts file error in TypeScript project: How to solve the error in file extension not being recognized and import statement?

Problems and solutions encountered when using ts-node to run .ts files in TypeScript projects

This article analyzes TypeError: Unknown file extension ".ts" and SyntaxError: Cannot use import statement outside a module error encountered when running TypeScript files containing class definitions and inheritance using ts-node, and provides a solution.

First, TypeError: Unknown file extension ".ts" indicates that ts-node cannot recognize .ts files, which is related to the module system configuration of Node.js. SyntaxError: Cannot use import statement outside a module indicates that ES module syntax ( import statement) is used in the CommonJS environment.

The root cause of the problem lies in "type": "module" configuration in package.json . This configuration states that the project uses an ES module system, and ts-node may have compatibility issues when handling ES modules. After deleting "type": "module" , ts-node tries to parse using CommonJS method, but CommonJS does not support import statements, so it still reports an error.

Solution: Coordinate compatibility between ES module and CommonJS module.

1. Modify tsconfig.json : add "esModuleInterop": true . This allows the TypeScript compiler to handle interoperability between ES modules and CommonJS modules.

2. Use ts-node-esm : Run the test file using the ts-node-esm test/testPerson.ts command in the ES module environment to ensure that ts-node executes the code in the correct module parsing method.

Therefore, by setting "esModuleInterop": true in tsconfig.json and using ts-node-esm command, import statement error and file extension recognition issues can be solved. As for "type": "module" in package.json , whether it is retained depends on whether the project needs to be compatible with ES modules. If not required, you can remove the configuration and make sure the code is compatible with CommonJS.

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