Koa

Koa is is largely based on Express, which in turn is based on Connect, a low-level middleware for creating Node.js Web applications.

Unlike those two aforementioned solutions, Koa's code doesn't include middleware within its core directly, but only provides the basic method for dealing callbacks, errors, external middleware loading, and so on.

So basically Koa is just the frame on which JavaScript middleware runs on, making the framework less error-prone and easier to maintain.

Since all middleware is loaded as modules it also makes the application's core code a lot less smaller, allowing developers to skip loading, executing and navigating through code they don't usually need.

What is new in this release:

• Added res.append()

What is new in version 0.21.0:

• Added res.append()

What is new in version 0.20.0:

• Added res.append()

What is new in version 0.19.0:

• Added res.append()

What is new in version 0.18.0:

• Added res.append()

What is new in version 0.15.0:

• Added this.href.

What is new in version 0.13.0:

• Custom status support via statuses.

What is new in version 0.11.0:

• Fixed app.use() assertion.

What is new in version 0.10.0:

• Added ctx.throw(err, object) support.
• Added ctx.throw(err, status, object) support.

What is new in version 0.8.0:

• Added this.response.is()
• Removed .status=string and res.statusString.

What is new in version 0.7.0:

• Refactored this.response.vary() to use vary
• Removed this.response.append()

What is new in version 0.6.0:

• Added nicer error formatting.
• Added assert object type in ctx.onerror.
• Changed .status default to 404.
• Removed .outputErrors, suppress output when handled by the dev.

What is new in version 0.5.1:

• Added request.hostname(getter).
• Removed response.charset and ctx.charset (too confusing in relation to ctx.type).
• Fixed a debug() name.

What is new in version 0.2.0:

• Added GeneratorFunction assertion for app.use().
• Refactored: move .is() to type-is.
• Refactored: move content negotiation to "accepts".
• Refactored: allow any streams with .pipe method.
• Removed next in callback for now.

Requirements:

• Node.js 0.11.9 or higher