review eslint core rules: disallow null comparisons without type-checking operators

Author: zloirock

packages/core-js-builder/index.js

@@ -36,7 +36,7 @@ module.exports = async function ({
   if (!['bundle', 'cjs', 'esm'].includes(format)) throw TypeError('Incorrect output type');
   summary = { comment: normalizeSummary(summary.comment), console: normalizeSummary(summary.console) };
 
-  const TITLE = filename != null ? filename : '`core-js`';
+  const TITLE = filename !== null || filename !== undefined ? filename : '`core-js`';
   let script = banner;
   let code = '\n';
 
@@ -95,7 +95,7 @@ module.exports = async function ({
     } else console.log('\u001B[36mnothing\u001B[0m');
   }
 
-  if (filename != null) {
+  if (!(filename === null || filename === undefined)) {
     await mkdirp(dirname(filename));
     await writeFile(filename, script);
   }

packages/core-js-compat/compat.js

@@ -56,7 +56,7 @@ module.exports = function ({
   version = null,
   inverse = false,
 } = {}) {
-  if (modules == null) modules = filter;
+  if (modules === null || modules === undefined) modules = filter;
   inverse = !!inverse;
 
   const parsedTargets = targets ? targetsParser(targets) : null;

packages/core-js/internals/regexp-sticky-helpers.js

@@ -8,7 +8,7 @@ var $RegExp = global.RegExp;
 var UNSUPPORTED_Y = fails(function () {
   var re = $RegExp('a', 'y');
   re.lastIndex = 2;
-  return re.exec('abcd') != null;
+  return re.exec('abcd') !== null;
 });
 
 // UC Browser bug
@@ -21,7 +21,7 @@ var BROKEN_CARET = UNSUPPORTED_Y || fails(function () {
   // https://bugzilla.mozilla.org/show_bug.cgi?id=773687
   var re = $RegExp('^r', 'gy');
   re.lastIndex = 2;
-  return re.exec('str') != null;
+  return re.exec('str') !== null;
 });
 
 module.exports = {

tests/eslint/eslint.config.js

@@ -154,6 +154,8 @@ const base = {
   'no-empty-function': ERROR,
   // disallow empty static blocks
   'no-empty-static-block': ERROR,
+  // disallow `null` comparisons without type-checking operators
+  'no-eq-null': ERROR,
   // disallow use of eval()
   'no-eval': ERROR,
   // disallow adding to native types