TypeScript Tricks

Modules

TS Module Resolution

Module Resolution Strategies

TypeScript module resolution supports node and classic strategies.

Introduction to Module Resolution

Module resolution is a crucial part of the TypeScript compilation process, as it determines how modules are located and linked to your code. TypeScript supports two primary module resolution strategies: node and classic. Understanding these strategies is essential for configuring your development environment and ensuring that your TypeScript code compiles successfully.

Node Module Resolution Strategy

The node module resolution strategy is inspired by Node.js module resolution logic. It is the default strategy in TypeScript and is generally preferred for most projects, especially when using npm or yarn for package management.

In this strategy, when a module is imported, TypeScript follows these steps:

  • Check if the module name is a path. If so, resolve it relative to the importing file.
  • If the module is not a path, TypeScript looks for a matching .ts, .tsx, .d.ts, or .js file in the node_modules directory.

Classic Module Resolution Strategy

The classic module resolution strategy was originally designed for the early TypeScript adoption phase. It is simpler but less capable than the node strategy, as it does not resolve modules from node_modules.

In this strategy, TypeScript follows these steps:

  • Resolve the module as a relative path if the module name starts with ./ or ../.
  • If it is not a relative path, TypeScript searches for the module in the same directory as the importing file and then traverses up the directory tree.

Choosing the Right Strategy

The choice between node and classic module resolution strategies typically depends on your project setup. If you are working with Node.js or use npm packages, the node strategy is recommended. The classic strategy may be suitable for legacy projects or when migrating older JavaScript projects to TypeScript.

You can specify the module resolution strategy in the tsconfig.json file:

Conclusion

Understanding TypeScript's module resolution strategies is vital for efficient module management and code organization. By choosing the appropriate strategy, you can ensure that your modules are correctly resolved, which is crucial for the success of your TypeScript projects.

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