traceur-annotations

/* jshint esnext: true */

traceur-annotations

A shim for Traceur's annotations. Can be used directly as an annotation in Traceur:

var Foo = Annotation.extend();
@Foo function bar() {}

or as a regular function in ES5/CoffeeScript/etc.:

Foo = Annotation.extend()
Foo bar = ->

Traceur instantiates the class and adds it to the annotatee's annotations array, so we simulate that in other environments.

class Annotation { init() {} }

has :: Object → Maybe Annotation

If the object is annotated with this annotation, return the instance. Otherwise, return undefined.

Annotation.has = function (obj) {
    return (obj.annotations || []).find((a) => a instanceof this);
};

extend :: Object → typeof Annotation

Create a new annotation based on this one. Can't do this with regular subclassing, as we wouldn't be able to dynamically delegate to the original class if we need to instantiate it ourselves without resorting to arguments.callee.

Annotation.extend = function (proto = {}) {
    var sub = class extends this {
        constructor(...args) {
            if(this instanceof Annotation) {
                this.init(...args);
            } else {
                var obj = args.pop() || this;
                obj.annotations = obj.annotations || [];
                obj.annotations.push(new sub(...args));
                return obj; // for chaining
            }
        }
    };
    Object.assign(sub.prototype, proto);
    return sub;
};
 
module.exports = Annotation;