Angular生产构建为何需设置--aot false？JIT有何优势？

Great question—AOT's benefits like pre-compiled, ready-to-run apps and early template error catching seem like a no-brainer, so it's totally reasonable to wonder why JIT is still an option, and why it's the default for ng build and ng serve. Let's break this down:

JIT's Key Advantages (AKA AOT's Tradeoffs) #

Even though AOT is ideal for most production scenarios, JIT shines in specific cases:

• Faster development iteration: AOT compiles all templates to JavaScript during the build process, which adds significant time to each build. For ng serve, JIT's runtime compilation means hot reloads are way quicker—critical for keeping your development flow smooth, especially in large projects where AOT build times can become a bottleneck.
• Dynamic template support: If your app relies on dynamic template generation (e.g., fetching template strings from an API, or assembling templates at runtime based on user input), AOT won't work. AOT requires all templates to be known and pre-compiled at build time, while JIT can compile these dynamic templates on the fly in the browser.
• Better debugging experience: AOT outputs optimized, minified JavaScript that's hard to map back to your original component and template code. JIT keeps the code closer to your source, making error messages more intuitive and debugging sessions less frustrating when you're tracking down template issues.
• Lower build resource usage: AOT compilation is more CPU and memory-intensive. On underpowered development machines or resource-constrained CI/CD pipelines, JIT can avoid build timeouts or out-of-memory errors that might occur with AOT.

Why ng build and ng serve Don't Default to AOT #

• Development-first defaults: Angular CLI is optimized for developer experience first. ng serve is meant for active development, where fast feedback and easy debugging matter more than pre-compiled performance. For ng build, the default is a development build (not production—--prod enables AOT by default), so JIT is the natural choice to speed up quick code validation.
• Lower barrier to entry: Early Angular versions had more AOT compatibility quirks, and strict template checks in AOT can throw errors that JIT ignores. Keeping JIT as the default helps new developers and legacy projects avoid immediate roadblocks, letting them adopt AOT once they're comfortable with the framework.

内容的提问来源于stack exchange，提问作者curiousBoy