betterpenthouse/lib/postformatting/rule-selector-remover.js

Generate critical path CSS for web pages

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = ruleSelectorRemover;

var _cssTree = _interopRequireDefault(require("css-tree"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

function ruleSelectorRemover(ast, selectorNodeMap, selectors) {
  selectors = new Set(selectors);

  _cssTree.default.walk(ast, {
    visit: 'Rule',
    enter: function (rule, item, list) {
      // remove a rule with a bad selector
      if (rule.prelude.type !== 'SelectorList') {
        list.remove(item);
        return;
      } // filter out non-critical selectors


      rule.prelude.children = rule.prelude.children.filter((selectorNode, item, list) => {
        let decision = selectorNodeMap.get(selectorNode);

        if (typeof decision === 'string') {
          decision = selectors.has(decision);
        }

        return typeof decision !== 'boolean' || decision;
      }); // remove the rule if no selector is left

      if (rule.prelude.children.isEmpty()) {
        list.remove(item);
      }
    }
  });
}