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eslint/no-unassigned-vars Correctness

✅ This rule is turned on by default.

What it does

Disallow let or var variables that are read but never assigned.

Ignored Files

This rule ignores .svelte and .vue files entirely. Oxlint only parses the <script> blocks of these files, so a binding that the template assigns looks like it is never assigned. In Svelte the template writes through bind:this={el} and bind:value={x}; in Vue a <script setup> let is a setup-let binding that v-model="x" and inline handlers such as @click="x = 1" assign to directly.

Why is this bad?

This rule flags let or var declarations that are never assigned a value but are still read or used in the code. Since these variables will always be undefined, their usage is likely a programming mistake.

Examples

Examples of incorrect code for this rule:

let status;
if (status === "ready") {
  console.log("Ready!");
}

Examples of correct code for this rule:

let message = "hello";
console.log(message);

let user;
user = getUser();
console.log(user.name);

How to use

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

Config (.oxlintrc.json)

{
  "rules": {
    "no-unassigned-vars": "error"
  }
}

Config (oxlint.config.ts)

import { defineConfig } from "oxlint";

export default defineConfig({
  rules: {
    "no-unassigned-vars": "error",
  },
});

CLI

oxlint --deny no-unassigned-vars

Version

This rule was added in v1.10.0.

References

• Rule Source
• Upstream rule docs
• Open rule in Oxc Playground