eventName should be an object to support multiple event names: see code below taken from Backbone code base

// Bind an event to a `callback` function. Passing `"all"` will bind
    // the callback to all events fired.
    on: function(name, callback, context) {
      if (!eventsApi(this, 'on', name, [callback, context]) || !callback) return this;

========
  // Implement fancy features of the Events API such as multiple event
  // names `"change blur"` and jQuery-style event maps `{change: action}`
  // in terms of the existing API.
  var eventsApi = function(obj, action, name, rest) {
    if (!name) return true;

    // Handle event maps.
    if (typeof name === 'object') {
      for (var key in name) {
        obj[action].apply(obj, [key, name[key]].concat(rest));
      }
      return false;
    }

Signed-off-by: areel <aidanreel@gmail.com>

backbone/backbone.d.ts

@@ -67,7 +67,7 @@ declare module Backbone {
     }
 
     class Events {
-        on(eventName: string, callback: (...args: any[]) => void , context?: any): any;
+        on(eventName: any, callback: (...args: any[]) => void , context?: any): any;
         off(eventName?: string, callback?: (...args: any[]) => void , context?: any): any;
         trigger(eventName: string, ...args: any[]): any;
         bind(eventName: string, callback: (...args: any[]) => void , context?: any): any;