Oxc
← Back to rules

eslint/eqeqeq Pedantic

⚠️ 🛠️ A dangerous auto-fix is available for this rule for some violations.

Purpose ​

Require the use of === and !== operators, and disallow == and !=.

Why is this bad? ​

Using non-strict equality operators can lead to unexpected behavior due to type coercion, causing hard-to-find bugs.

Examples ​

JSON configuration example:

json
{
  "eqeqeq": ["error", "always", { "null": "ignore" }]
}

"always" (default) ​

Incorrect code examples for this rule:

js
/* eqeqeq: "error" */

if (x == 42) {
}
if ("" == text) {
}
if (obj.getStuff() != undefined) {
}

Correct code examples for this rule:

js
/* eqeqeq: "error" */

if (x === 42) {
}
if ("" === text) {
}
if (obj.getStuff() !== undefined) {
}

"smart" ​

With the "smart" option, incorrect code examples for this rule:

js
/* eqeqeq: ["error", "smart"] */

if (x == 42) {
}
if ("" == text) {
}

With the "smart" option, correct code examples for this rule:

js
/* eqeqeq: ["error", "smart"] */

if (typeof foo == "undefined") {
}
if (foo == null) {
}
if (foo != null) {
}

{"null": "ignore"}（when the first option is "always"） ​

With the { "null": "ignore" } option, incorrect code examples for this rule:

js
/* eqeqeq: ["error", "always", { "null": "ignore" }] */
if (x == 42) {
}
if ("" == text) {
}

With the { "null": "ignore" } option, correct code examples for this rule:

js
/* eqeqeq: ["error", "always", { "null": "ignore" }] */
if (foo == null) {
}
if (foo != null) {
}

{"null": "always"}（default - when the first option is "always"） ​

With the { "null": "always" } option, incorrect code examples for this rule:

js
/* eqeqeq: ["error", "always", { "null": "always" }] */

if (foo == null) {
}
if (foo != null) {
}

With the { "null": "always" } option, correct code examples for this rule:

js
/* eqeqeq: ["error", "always", { "null": "always" }] */

if (foo === null) {
}
if (foo !== null) {
}

{"null": "never"}（when the first option is "always"） ​

With the { "null": "never" } option, incorrect code examples for this rule:

js
/* eqeqeq: ["error", "always", { "null": "never" }] */

if (x == 42) {
}
if ("" == text) {
}
if (foo === null) {
}
if (foo !== null) {
}

With the { "null": "never" } option, correct code examples for this rule:

js
/* eqeqeq: ["error", "always", { "null": "never" }] */

if (x === 42) {
}
if ("" === text) {
}
if (foo == null) {
}
if (foo != null) {
}

Configuration ​

1st option ​

Type: "always" | "smart"

"always" ​

Always require triple-equals comparisons, ===/!==. This is the default.

"smart" ​

Allow some safe comparisons to use ==/!= (typeof, literals, nullish values).

2nd option ​

This option is an object containing the following properties:

null ​

Type: "always" | "never" | "ignore"

Configuration for whether comparisons with null are allowed/forbidden, for example foo == null or foo != null

"always" ​

Always require triple-equals when comparing with null, === null/!== null. This is the default.

"never" ​

Never require triple-equals when comparing with null; always use == null/!= null.

"ignore" ​

Ignore null comparisons and allow either == null/!= null or === null/!== null.

How to use ​

To enable this rule using the config file or in the CLI, you can use:

json
{
  "rules": {
    "eqeqeq": "error"
  }
}
ts
import { defineConfig } from "oxlint";

export default defineConfig({
  rules: {
    "eqeqeq": "error",
  },
});
bash
oxlint --deny eqeqeq

Version ​

This rule was added in v0.0.3.

References ​

© 2026 VoidZero Inc. and Oxc contributors.