What is the difference between Promise.all and Promise.allSettled?

Promise.all

Rejects immediately if ANY promise rejects.

Promise.all([
  Promise.resolve(1),
  Promise.reject('error'),
  Promise.resolve(3)
])
.then(results => console.log(results))
.catch(err => console.log(err)); // 'error'

Promise.allSettled

Waits for ALL promises, never rejects.

Promise.allSettled([
  Promise.resolve(1),
  Promise.reject('error'),
  Promise.resolve(3)
])
.then(results => console.log(results));
// [
//   { status: 'fulfilled', value: 1 },
//   { status: 'rejected', reason: 'error' },
//   { status: 'fulfilled', value: 3 }
// ]

When to Use Each:

Promise.all: When you need ALL promises to succeed (fail-fast)

• Fetching data that all depends on each other
• Validation where any failure should stop

Promise.allSettled: When you want results regardless of failures

• Batch operations where some can fail
• Collecting results from multiple sources