code: function create_node(length) {
  	const node = {};
  	Object.defineProperty(node, "_", {
  		value: {
  			length: length, //record array length
  			watchers: {},
  			watcher_key: new Set(),
  			watcher_props: new Set(),
  			on_watch_callback: undefined
  		},
  		writable: true,
  		enumerable: false
  	});
  
  	return node;
  }
docs: Create a node
  @param {*} [length]