Backbone with decorators (warning: untested) *update*: corrections from Ben applied.

00_decorators.js

import _ from 'underscore';

export function on(eventName){
  return function(target, name, descriptor){
    if(!target.events) {
        target.events = {};
    }
    if(_.isFunction(target.events)) {
        throw new Error('The on decorator is not compatible with an events method');
        return;
    }
    if(!eventName) {
        throw new Error('The on decorator requires an eventName argument');
    }
    target.events[eventName] = name;
    return descriptor;
  }
}

01_view.js

import { ItemView } from 'backbone.marionette';
import { on } from '../utils/decorators';
import FormTemplate from '../templates/FormTemplate';

class FormView extends ItemView {
  static template = FormTemplate;
  
  @on("click .button")
  submitForm(e){
    e.preventDefault();
    
    console.log("I'm a teapot!");
  }
}

@StevenLangbroek this is still awesome. I tested it though, and it doesn't look like it works exactly like this. The constructor hasn't run when decorators are evaluated, which causes issues for delegateEvents (which needs an $el value.

I wrote an alternative version that is a bit more verbose, but is working for me:

export function on(eventName){
  return function(target, name, descriptor){
    if(!target.events) {
        target.events = {};
    }
    if(_.isFunction(target.events)) {
        throw new Error('The on decorator is not compatible with an events method');
        return;
    }
    if(!eventName) {
        throw new Error('The on decorator requires an eventName argument');
    }
    target.events[eventName] = name;
    return descriptor;
  }
}

I can just use the events hash since it won't have been evaluated yet. This does make this incompatible with events functions, but I don't think you'd want to mix the decorators syntax with an events function anyway.