no-leaked-timeout

Full Name in eslint-plugin-react-web-api

react-web-api/no-leaked-timeout

Full Name in @eslint-react/eslint-plugin

@eslint-react/web-api-no-leaked-timeout

Presets

web-api recommended recommended-typescript recommended-type-checked strict strict-typescript strict-type-checked

Rule Details

Scheduling a timeout within the setup function of useEffect without canceling it in the cleanup function can lead to unwanted setTimeout callback executions and may also result in stale values captured by previous renders' effects after each subsequent re-render.

Common Violations

Invalid

import React, { useEffect, useState } from "react";

function MyComponent() {
  const [count, setCount] = useState(0);

  useEffect(() => {
    const timeoutId = setTimeout(() => console.log(count), 1000);
    //                ^^^ A 'setTimeout' created in 'useEffect' must be cleared in the cleanup function.
  }, []);

  return null;
}

Valid

import React, { useEffect, useState } from "react";

function MyComponent() {
  const [count, setCount] = useState(0);

  useEffect(() => {
    const timeoutId = setTimeout(() => console.log(count), 1000);
    return () => clearTimeout(timeoutId);
  }, []);

  return null;
}

Resources

• Rule Source
• Test Source

Further Reading

• MDN: setTimeout
• MDN: clearTimeout
• React Docs: Synchronizing with effects

See Also

• react-web-api/no-leaked-event-listener
  Enforces that every addEventListener in a component or custom hook has a corresponding removeEventListener.
• react-web-api/no-leaked-interval
  Enforces that every setInterval in a component or custom hook has a corresponding clearInterval.
• react-web-api/no-leaked-resize-observer
  Enforces that every ResizeObserver created in a component or custom hook has a corresponding ResizeObserver.disconnect().