Setting context props at specific DOM tree levels on elements.

dom-context.js

const _context = Symbol();
let currentContext = null;

function getContext (elem) {
  elem.dispatchEvent(new Event('__context', {
    bubbles: true,
    cancelable: true,
    composed: true,
    scoped: true
  }));
  const returnContext = currentContext;
  currentContext = null;
  return returnContext;
}

function setContext (elem, context) {
  if (!elem.hasOwnProperty(_context)) {
    elem.addEventListener('__context', function (e) {
      e.stopPropagation();
      currentContext = this[_context];
    });
  }
  elem[_context] = context;
}