annotations.md

Annotations

This module provides tools to play with annotations.

AOP

A aopAnnotation function is provided to allow you to use Aspect-Oriented Programming with Javascript decorators. Its interface is designed to make its use familiar for those used to Express or Go's HTTP middleware.

The goal of this helper is to help remove logic from a method body when it can make it more readable.

Here is a simple example:

// Log method input and output
function Log(title: string): Function {
    return aopAnnotation((next, args) => {
        console.log(`${title} - Input: `, ...args)
        const result = next(args)
        console.log(`${title} - Output: `, result)
        return result
    })
}

class AopTest {
    @Log('LOG')
    foo(nb: int): string {
        console.log('Computing...')
        return nb * 2
    }
}

const aopTest = new AopTest()
aopTest.foo(2)

Console output:

LOG - Input: 2
Computing...
LOG - Output: 4

Other example uses of this helper are Beemo's conversion and validation annotations.