2.8 KiB
THIS DOCUMENT IS IN PROGRESS. THIS PARAGRAPH SHALL BE REMOVED WHEN THIS DOCUMENT IS DONE.
TO DO:
- Remove benchmark from readme
Koa vs Express
Does Koa replace Express?
It's more like Connect, but a lot of the Express goodies were moved to the middleware level in Koa to help form a stronger foundation. This makes middleware more enjoyable and less error-prone to write, for the entire stack, not just the end application code.
Typically many middleware would re-implement similar features, or even worse incorrectly implement them, when features like signed cookie secrets among others are typically application-specific, not middleware specific.
Does Koa replace Connect?
No, just a different take on similar functionality now that generators allow us to write code with less callbacks. Connect is equally capable, and some may still prefer it, it's up to what you prefer.
Why isn't Koa just Express 4.0?
Koa is a pretty large departure from what people know about Express, the design is fundamentally much different, so the migration from Express 3.0 to this Express 4.0 would effectively mean rewriting the entire application, so we thought it would be more appropriate to create a new library.
Is Koa faster than Express?
To our amazement, yes, but only if you use yield *next. We do not provide examples of using delegated yields as we find it confusing as well as unnecessary for most people. Here are Koa's benchmarks when using delegated yields:
1 middleware
8849.36
5 middleware
8685.74
10 middleware
8511.08
15 middleware
8456.86
20 middleware
8211.93
30 middleware
8102.98
50 middleware
7617.67
100 middleware
6899.45
Here are the benchmarks for Express:
1 middleware
7805.19
5 middleware
7707.15
10 middleware
7475.08
15 middleware
7261.73
20 middleware
7012.07
30 middleware
6672.76
50 middleware
6255.92
100 middleware
5000.98
Also note that Express uses many more middleware than Koa, so these benchmarks are largely in Koa's favor.
How is Koa different than Connect/Express?
Generated-based control flow
Thanks to co.
No callback hell.
Better error handling through try/catch.
No need for domains.
Koa is barebone
Unlike both Connect and Express, Koa does not include any middleware.
Unlike Express, routing is not provided.
Unlike Express, many convenience utilities are not provided. For example, sending files.
More modular.
Koa relies less middleware
For example, instead of a "body parsing" middleware, you would instead use a body parsing function.
Koa abstracts node's request/response
Less hackery.
Proper stream handling.