obj.listenTo([bindTarget,] event, handler)

.listenTo is useful for creating bindings that can can be torn down with stopListening. This is useful when creating rich behaviors that can't be accomplished using computed values, or if you are trying to avoid streams.

For example, the following creates an observable that counts how many times its name property has changed:

class Person {
  constructor(){
    this.nameChanged = 0;
    this.listenTo("name", function(){
      this.nameChanged++;
    })
  },
  setName(newVal) {
    this.name = newVal;
    this.dispatch("name",[newVal])
  }
}
mixinMapBindings(Person.prototype);

var person = new Person();
person.setName("Justin");
person.setName("Ramiya");
person.nameChanged //-> 2

.listenTo event bindings are stored on an observable and MUST be unbound using stopListening. .stopListening make it easy to unbind all of the .listenTo event bindings when the observable is no longer needed:

person.stopListening();

If no bindTarget is passed, .listenTo binds to the current observable.

can-component's connectedCallback lifecyle hook is often used to call .listenTo to setup bindings that update viewmodel properties.