@html-eslint/eslint-plugin/lib/rules/no-multiple-h1.js

ESLint plugin for html

/**
 * @typedef { import("../types").RuleModule<[]> } RuleModule
 * @typedef { import("@html-eslint/types").Tag } Tag
 */

const { RULE_CATEGORY } = require("../constants");

const MESSAGE_IDS = {
  MULTIPLE_H1: "unexpectedMultiH1",
};

/**
 * @type {RuleModule}
 */
module.exports = {
  meta: {
    type: "code",

    docs: {
      description: "Disallow multiple `<h1></h1>`.",
      category: RULE_CATEGORY.SEO,
      recommended: true,
    },

    fixable: null,
    schema: [],
    messages: {
      [MESSAGE_IDS.MULTIPLE_H1]: "Unexpected multiple `<h1></h1>`.",
    },
  },

  create(context) {
    /**
     * @type {Tag[]}
     */
    const h1s = [];

    return {
      Tag(node) {
        if (node.name === "h1") {
          h1s.push(node);
        }
      },
      "Document:exit"() {
        if (h1s.length > 1) {
          h1s.forEach((h1) => {
            context.report({
              node: h1,
              messageId: MESSAGE_IDS.MULTIPLE_H1,
            });
          });
        }
      },
    };
  },
};