lite-signal

lite-signal provides basic publish-subscribe functionality for Polymer 2.

It is a descendant of the unmaintained https://github.com/PolymerElements/iron-signals component.

Note: avoid using lite-signal whenever you can use a controller (parent element) to mediate communication instead.

To send a signal, fire a custom event of type lite-signal, with a detail object containing name and data fields.

this.dispatchEvent(
  new CustomEvent("lite-signal", {
    bubbles: true,
    compose: true, // to cross Shadow DOM boundaries
    detail: {
      name: "hello",
      data: { foo: true }
    }
  })
)

To receive a signal, listen for lite-signal-<name> event on a lite-signal element within your Polymer element:

<lite-signal on-lite-signal-hello="helloSignalHandler"></lite-signal>

...


helloSignalHandler(e) {
  // do something with event
}

You can fire a signal event from anywhere, and all lite-signal elements will receive the event, regardless of where they are in DOM.