旧网站迁移至Angular2：拆分小项目再合并是否可行？求参考示例

Great question—migrating a legacy site to Angular 2 (now part of the broader Angular framework) can feel overwhelming, so breaking the work into small, independent projects before merging is absolutely a strong approach, and in many cases, it’s one of the lowest-risk strategies you can use. Let’s break this down:

Is the "small projects first, then merge" approach optimal? #

Yes, and here’s why it works so well for legacy migrations:

• Incremental risk reduction: Instead of rewriting your entire site in one go (which can lead to costly delays or catastrophic failures if something goes wrong), you can validate each small project’s functionality, performance, and integration with your legacy systems before moving on. This lets you fix issues early, when they’re easier to address.
• Parallel development: If you have a team, different members can work on separate modules (e.g., a user authentication module, a product listing module) without stepping on each other’s toes. This speeds up the overall migration timeline.
• Minimal disruption to the live site: You can keep your legacy site running while building and testing each Angular module. Once a module is ready, you can gradually replace the corresponding legacy section, rather than doing a full "big bang" switchover.

That said, you’ll need to plan ahead to avoid headaches during the merge:

• Standardize dependencies and tooling: Make sure all small projects use the same version of Angular, shared libraries (like RxJS or NgRx), and build tools (Angular CLI). This prevents version conflicts when merging.
• Define clear boundaries for modules: Each small project should focus on a single, self-contained feature (e.g., "checkout flow" instead of "all e-commerce features"). This makes merging simpler and keeps your codebase organized.
• Plan for shared services early: If multiple modules need access to common functionality (like API calls or user session management), build a shared core module first and have all small projects depend on it. This avoids duplicating code and eases integration later.

Where to find practical examples to avoid risks #

While I can’t link to external resources directly, here are reliable places to look within the Angular ecosystem and community:

• Angular Official Documentation: The Angular docs have a dedicated section on incremental migration, including step-by-step guides for embedding Angular components into legacy pages (using tools like Angular Elements) and gradually scaling to full modules. These examples cover common pitfalls like handling cross-framework communication and state management.
• Community Tutorials and Case Studies: Many developers and companies share their migration stories in blog posts (search for "Angular legacy migration modular approach"). These often include real-world examples of splitting a legacy site into small Angular projects, merging them into a single workspace, and solving issues like routing integration or dependency conflicts.
• Angular CLI Workspace Examples: Use the Angular CLI to create a multi-project workspace (ng new --create-application false), then add small feature projects to it. This structure mirrors the "small projects first" approach and lets you practice merging modules within a controlled environment. You can find built-in examples of shared modules and cross-project dependencies in the CLI’s default workspace setup.
• Open-Source Repositories: Look for open-source projects that started as legacy sites and migrated to Angular incrementally. Studying their commit history and module structure can show you how they split features, managed shared code, and eventually merged everything into a single codebase.

Quick Risk-Mitigation Tips #

• Use a monorepo tool like Nx (built for Angular) to manage your small projects from the start. It enforces consistency and makes merging modules far smoother.
• Write unit tests and end-to-end tests for each small project. This ensures that when you merge, you don’t break existing functionality.
• Start with the least critical features first. This lets you learn the migration process without risking your site’s core functionality.

内容的提问来源于stack exchange，提问作者Nestor