code: function isNullOrUndefined(node) {
  		return (node.type === "Literal" && node.value === null) ||
  			(node.type === "Identifier" && node.name === "undefined") ||
  			(node.type === "UnaryExpression" && node.operator === "void");
  	}
docs: Checks whether or not a node is 'null' or 'undefined'.
  
  @param {ASTNode} node - A node to check.
  @returns {boolean} Whether or not the node is a 'null' or 'undefined'
  @public