Promise.then() Handle fulfillment
Last updated: 2026-09-09
Promise.then() Handle fulfillment
then registers a fulfillment callback and returns a new Promise for chaining.
| Category | Async |
|---|---|
| ES version | ES6 |
📝 Syntax
promise.then((value) => { ... });⚙️ Parameters
| onFulfilled | Callback for fulfillment, receives the resolved value. |
|---|---|
| onRejected | Optional. Callback for rejection. |
Returns：A new Promise (chainable).
Mutates the original：No (returns a new value)
▶ Example
Edit the code, press Run, and see the result in the output panel:
💡 Tip then returns a new Promise for chaining — each return value feeds the next.
⚠️ Warning Forgetting to return in then passes undefined to the next.
🌐 Browser support
| Browser |  Chrome |
 Edge |
 Firefox |
 Safari |
 Opera |
|---|---|---|---|---|---|
| Promise.then() | ✓ v32 | ✓ v12 | ✓ v27 | ✓ v8 | ✓ v19 |
| Supported by all modern browsers | |||||
🏷️ Related Items
💡 Related Cases
More case studies coming soon — check back later.
📚 Related Tutorials
❓ FAQ
QWhen does the then callback run?
AAfter the Promise resolves (microtask queue).
QHow many times can then chain?
AUnlimited — each then returns a new Promise.
Qthen vs async/await?
Aasync/await is cleaner — prefer it for new code.
