tools/lint/eslint/eslint-plugin-mozilla/lib/rules/use-includes-instead-of-indexOf.js


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/**
 * @fileoverview Use .includes instead of .indexOf
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

"use strict";

// -----------------------------------------------------------------------------
// Rule Definition
// -----------------------------------------------------------------------------

module.exports = function(context) {
  // ---------------------------------------------------------------------------
  // Public
  //  --------------------------------------------------------------------------

  return {
    BinaryExpression(node) {
      if (
        node.left.type != "CallExpression" ||
        node.left.callee.type != "MemberExpression" ||
        node.left.callee.property.type != "Identifier" ||
        node.left.callee.property.name != "indexOf"
      ) {
        return;
      }

      if (
        (["!=", "!==", "==", "==="].includes(node.operator) &&
          node.right.type == "UnaryExpression" &&
          node.right.operator == "-" &&
          node.right.argument.type == "Literal" &&
          node.right.argument.value == 1) ||
        ([">=", "<"].includes(node.operator) &&
          node.right.type == "Literal" &&
          node.right.value == 0)
      ) {
        context.report(node, "use .includes instead of .indexOf");
      }
    },
  };
};