seniorjQuery
What are Deferred objects in jQuery and how do they compare to native Promises?
Updated May 14, 2026
Short answer
Deferred objects are jQuery's abstraction for asynchronous workflows, similar to Promises but with older semantics and additional control methods.
Deep explanation
Before native JavaScript Promises became standardized, jQuery introduced Deferred objects to simplify asynchronous programming.
A Deferred represents a future value or asynchronous operation.
Core methods:
- resolve()
- reject()
- notify()
- done()
- fail()
- always()
- then()
Differences from native Promises:
- Deferreds are mutable while Promises are immutable.
- Deferreds support progress notifications.
- Promise behavior is more standardized.
- Deferred chaining behavior historically differed from Promise/A+ specifications.…
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