ES7-Aspect


This library provides simple aspect oriented programming features in javascript using ES7 decorators.

It is a derivative of Board project.

Please note that this library is intended to do simple runtime checks and should be used as the last resort. __It is not async-compatible, i.e. the activities in an Aspect class cannot contain any callbacks or promises, whereas the original function can be async.__

Sample Usage

In gru-aspect.js:
``javascript
import Aspect from 'es7-aspect';

export default class GruAspect extends Aspect {
//Once again, no async calls in any of these functions

@Aspect.before('stealsTheMoon')
eatsABanana(bananas) {
if (bananas) {
console.log(There're ${bananas.length} banana(s). Eat one.);
bananas.pop();
}
}

@Aspect.intercept('stealsTheMoon')
checkBananas(resolve, reject, bananas) {
if (!bananas || bananas.length === 0) {
console.log('No banana. Nah.');
reject();
}
else {
console.log(${bananas.length} banana(s)!);
resolve();
}
}

@Aspect.after('stealsTheMoon')
givesBananas(bananas) {
console.log(${bananas.length} banana(s) left.);
}
}
`

In gru.js:
`javascript
import Aspect from 'es7-aspect';
import GruAspect from './gru-aspect';

@Aspect.use(GruAspect)
export default class Gru {
stealsTheMoon(bananas) {
console.log('Just stole the moon!');
}
}
`

In a console:
`javascript
new Gru().stealsTheMoon();
// Prints 'No banana. Nah.'

new Gru().stealsTheMoon(['banana', 'banana']);
// Prints
// There're 2 banana(s). Eat one.
// Just stole the moon!
// 1 banana(s) left.
`




Advices

There are three advices: Before, After and Intercept.

$3

Perform certain activities before the original function executes. After all defined activities finishes, the original will run. _The pre-activities have access to the actual arguments that will be eventually applied._

$3

The intercept advice runs before the original function, similar to the before advice, __except that__ there can be one and only one intercept advice defined for a method, and it has the ability to prevent the original function from execution.
* To continue running after completing the interception, call resolve().
* Otherwise, to stop execution, call reject([val]). [val]` is an optional argument that will be used as the return value of original function.

$3

Perform certain activities after the original function executes. All activities run after the original function completes execution. _The post-activities have access to the actual arguments that will be eventually applied._