js/no-floating-promises

Why

save() without await runs on its own: the code after it does not wait, a failure becomes an unhandled rejection that the user never sees, and the order of updates is left to chance. items.forEach(async (item) => ...) is the same mistake in a loop: forEach ignores the promises.

Fix

await the call (or return it), or attach .catch() that shows or reports the error. Use for...of with await when order matters and Promise.all or Promise.allSettled when it does not. Mark a deliberate fire-and-forget with void save() and handle its errors inside. In a TypeScript project, turn on the typed lint rule @typescript-eslint/no-floating-promises; it finds these with type information that a text check cannot have.

Examples

// bad
button.addEventListener('click', () => { save(form); close() })
// good
button.addEventListener('click', async () => {
  try { await save(form); close() } catch (err) { showError(err) }
})

Sources

• MDN, Using promises (error handling and chaining)
• MDN, Promise (chained promises and error handling)

Read it in the terminal

npx github:dawidolko/frontend-skills explain js/no-floating-promises