lib/getCriticalRules.js
function clean(root) {
  var test = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 'critical-selector';

  var clone = root.clone();
  if (clone.type === 'decl') {
    clone.remove();
  } else {
    clone.walkDecls(test, function (decl) {
      decl.remove();
    });
  }
  return clone;
}
function clean(root) {
  var test = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 'critical-selector';

  var clone = root.clone();
  if (clone.type === 'decl') {
    clone.remove();
  } else {
    clone.walkDecls(test, function (decl) {
      decl.remove();
    });
  }
  return clone;
}
function clean ( root ) { var test = arguments . length > 1 && arguments [ 1 ] !== undefined ? arguments [ 1 ] : 'critical-selector' ; var clone = root . clone ( ) ; if ( clone . type === 'decl' ) { clone . remove ( ) ; } else { clone . walkDecls ( test , function ( decl ) { decl . remove ( ) ; } ) ; } return clone ; }
Clean a root node of a declaration.

@param {Object} root PostCSS root node.
@param {string} test Declaration string. Default  `critical-selector`
@return {Object} clone Cloned, cleaned root node.
Clean a root node of a declaration .