noop()

noop(): void

A function that does nothing and returns undefined.

Useful as a default callback or placeholder.

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Returns: void

Always returns undefined.

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Since

2.0.0

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Also known as

always (Ramda) · constVoid (Effect) · doNothing (Remeda) · noop (Lodash, es-toolkit, Radashi, Antfu) · ❌ (Modern Dash)

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Example

// Default callback to avoid null checks
function fetchData(onSuccess: () => void = noop) {
  // No need for: if (onSuccess) onSuccess()
  onSuccess();
}

// In tests
const handler: Arrayable<() => void> = [noop, noop];
expect(processItems(handler)).toHaveLength(2);

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How it works?

A function that does nothing and returns undefined.

Use Case: Default Callback

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Use Cases

Provide default callbacks 📌

Use as a placeholder for optional callback functions to avoid null checks. Essential for cleaner code and avoiding "if (callback)" checks.

#default#callbacks#placeholder#optional#safety#null-checks

function fetchData(onSuccess = noop) {
  // Safe to call even if not provided
  onSuccess();
}

fetchData(); // No error

Stub functions for testing 📌

Use as a placeholder for dependencies during unit testing. Useful for mocking functions that don't need to return values.

#stub#testing#mocking#placeholder#unit-tests#dependencies

const mockLogger = {
  info: noop,
  warn: noop,
  error: noop,
};

// Test logic without filling console with logs
processData(data, mockLogger);

Disable event handlers temporarily

Replace active handlers with noop to "mute" functionality without removing listeners. Useful for feature flags or temporary disabling during maintenance.

#disable#handlers#events#mute#temporary#feature-flags

let onNotification = showToast;

// Mute notifications during focus mode
function enableFocusMode() {
  onNotification = noop;
}

function disableFocusMode() {
  onNotification = showToast;
}

// Code doesn't need to check if handler exists
socket.on("notification", (msg) => onNotification(msg));