49 lines
2 KiB
Markdown
49 lines
2 KiB
Markdown
# Frequently Asked Questions
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## Does Koa replace Express?
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It's more like Connect, but a lot of the Express goodies
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were moved to the middleware level in Koa to help form
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a stronger foundation. This makes middleware more enjoyable
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and less error-prone to write, for the entire stack, not
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just the end application code.
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Typically many middleware would
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re-implement similar features, or even worse incorrectly implement them,
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when features like signed cookie secrets among others are typically application-specific,
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not middleware specific.
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## Does Koa replace Connect?
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No, just a different take on similar functionality
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now that async functions allow us to write code with fewer
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callbacks. Connect is equally capable, and some may still prefer it,
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it's up to what you prefer.
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## Does Koa include routing?
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No - out of the box Koa has no form of routing, however
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many routing middleware are available: https://github.com/koajs/koa/wiki
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## Why isn't Koa just Express 4.0?
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Koa is a pretty large departure from what people know about Express,
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the design is fundamentally much different, so the migration from
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Express 3.0 to this Express 4.0 would effectively mean rewriting
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the entire application, so we thought it would be more appropriate
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to create a new library.
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## What custom properties do the Koa objects have?
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Koa uses its own custom objects: `ctx`, `ctx.request`, and `ctx.response`.
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These objects abstract node's `req` and `res` objects with convenience methods and getters/setters.
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Generally, properties added to these objects must obey the following rules:
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- They must be either very commonly used and/or must do something useful
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- If a property exists as a setter, then it will also exist as a getter, but not vice versa
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Many of `ctx.request` and `ctx.response`'s properties are delegated to `ctx`.
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If it's a getter/setter, then both the getter and the setter will strictly
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correspond to either `ctx.request` or `ctx.response`.
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Please think about these rules before suggesting additional properties.
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