aurelia-templating-resources/src/self-binding-behavior.ts

/* eslint-disable @typescript-eslint/no-unused-vars */
import { bindingBehavior } from 'aurelia-binding';

function findOriginalEventTarget(event) {
  return (event.path && event.path[0]) || (event.deepPath && event.deepPath[0]) || event.target;
}

function handleSelfEvent(event) {
  let target = findOriginalEventTarget(event);
  if (this.target !== target) { return; }
  this.selfEventCallSource(event);
}

@bindingBehavior('self')
export class SelfBindingBehavior {
  bind(binding, source) {
    if (!binding.callSource || !binding.targetEvent) {
      throw new Error('Self binding behavior only supports event.');
    }
    binding.selfEventCallSource = binding.callSource;
    binding.callSource = handleSelfEvent;
  }

  unbind(binding, source) {
    binding.callSource = binding.selfEventCallSource;
    binding.selfEventCallSource = null;
  }
}