oxc-project/oxc · error · OxcDiagnostic

Prefer `EventTarget` over `EventEmitter`.

Error message

Prefer `EventTarget` over `EventEmitter`.

What it means

Diagnostic from the unicorn/prefer-event-target lint rule. It fires when `EventEmitter` (from `events` or a non-ignored package) is instantiated or used as a base class in code that is not Node-specific; the DOM-standard `EventTarget` is cross-environment and preferred. Packages in the rule's ignore list (e.g. `@angular/core`, `eventemitter3`) are exempt. It is a lint suggestion, not a runtime error.

Source

Thrown at crates/oxc_linter/src/rules/unicorn/prefer_event_target.rs:17

use oxc_ast::{
    AstKind,
    ast::{Argument, BindingPattern, Expression, IdentifierReference},
};
use oxc_diagnostics::OxcDiagnostic;
use oxc_macros::declare_oxc_lint;
use oxc_span::Span;

use crate::{
    AstNode, ast_util::get_declaration_of_variable, context::LintContext, rule::Rule,
    utils::is_import_from_module,
};

const IGNORED_PACKAGES: [&str; 2] = ["@angular/core", "eventemitter3"];

fn prefer_event_target_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Prefer `EventTarget` over `EventEmitter`.")
        .with_help("Change `EventEmitter` to `EventTarget`. EventEmitters are only available in Node.js, while EventTargets are also available in browsers.")
        .with_note("https://developer.mozilla.org/en-US/docs/Web/API/EventTarget")
        .with_label(span)
}

#[derive(Debug, Default, Clone)]
pub struct PreferEventTarget;

declare_oxc_lint!(
    /// ### What it does
    ///
    /// Prefers `EventTarget` over `EventEmitter`.
    ///
    /// This rule reduces the bundle size and makes your code more cross-platform friendly.
    ///
    /// See the [differences](https://nodejs.org/api/events.html#eventtarget-and-event-api) between `EventEmitter` and `EventTarget`.
    ///
    /// ### Why is this bad?

View on GitHub (pinned to e1e7af627c)

Solutions

1. Change `class X extends EventEmitter` to `extends EventTarget`
2. Switch `new EventEmitter()` to `new EventTarget()` and use `addEventListener`/`dispatchEvent` instead of `on`/`emit`
3. Remove the now-unused `events` import
4. Add a package to the rule's ignore list if `EventEmitter` is genuinely required

When it happens

Trigger: Thrown at crates/oxc_linter/src/rules/unicorn/prefer_event_target.rs:17 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of oxc-project/oxc@e1e7af627c (2026-08-20). Data as JSON: /api/errors/24450369aff63e9a. Report an issue: GitHub.