How to share code between TypeScript projects?

Sharing code across TypeScript projects is a common requirement, especially in large or multi-project environments. Here are several mainstream and efficient methods to achieve code sharing:

1. Creating a Shared Library

The most common and recommended approach is to create a shared TypeScript library. Package common functionalities, components, and models into a standalone library and manage it via package managers such as npm or yarn.

Steps:

• Initialize the library project: Use npm init or yarn init to create a new project.
• Develop and build: Develop your shared code in this project and compile it using tsc (TypeScript Compiler).
• Publish to package manager: Publish the compiled code to npm or a private npm registry.
• Integrate in other projects: Install and use the library in other TypeScript projects via npm install your-library-name.

Example:

Suppose you have a utility library that needs to be used across multiple projects:

typescript
// src/index.ts
export function add(a: number, b: number): number {
    return a + b;
}

After compiling and publishing, other projects can install and use this function via npm.

2. Using Monorepo for Project Management

Monorepo is a project management strategy that allows you to manage multiple related projects within a single repository. This is highly effective for sharing code because all projects reside in the same repository, making code sharing straightforward.

Recommended Tools:

• Lerna: Helps manage versions and dependencies across multiple packages.
• Yarn Workspaces: Also supports multi-package management and can effectively link various packages.

Example:

In a Monorepo using Lerna, you can easily reference one package as a dependency of another.

3. Using Git Submodules

If your projects are distributed across different repositories, consider using Git submodules to share code. By using Git submodules, you can include another repository as a subdirectory.

Steps:

• Add submodule: In your main project repository, use git submodule add <repository-url> to add the submodule.
• Update and manage: Submodules can be updated independently or alongside the main project.

This approach is suitable for scenarios where the shared code is minimal and updates are infrequent.

Summary

Each method has its own use cases; the choice of the most suitable method depends on your project structure and team workflow. Creating a shared library is suitable for most cases, especially when the code needs to be widely shared and reused; Monorepo is ideal for scenarios where projects are closely related; Git submodules are suitable for scenarios where projects are relatively independent but still need to share some code.