Promise chain
A promise chain is a sequence of linked promise reactions in which each step receives the preceding step’s fulfillment value or handles its rejection.
The Joy of JavaScript
A promise chain is a sequence of linked Promise reactions in which each step receives the result or failure of the previous step.
- How it is used
- Structures linear asynchronous flows as composable, forward-moving data transformations.
- How deep it goes
- Explains linking, settlement, nested-promise flattening, broken chains, error recovery, and finally, with runnable snippets.
- Examples
- Uses string transformations, nested promises, thrown errors, default recovery values, unhandled rejection warnings, and finally.
- What you can do after
- Builds linear Promise workflows, preserves nested results and failures, and diagnoses accidental disjoint chains.
Get Programming with JavaScript Next: New features of ECMAScript 2015, 2016, and beyond
A sequence of linked promise operations in which the outcome of one promise feeds subsequent handlers.
- How it is used
- Coordinates dependent asynchronous operations and handles their errors as a single flow.
- How deep it goes
- Works through a repeating image chain, its memory leak, and rejection propagation; stops short of broader promise internals.
- Examples
- Uses a random-image workflow that fetches, fades, pauses, and repeats, with a catch that restarts on failure.
- What you can do after
- Understand how linked handlers carry outcomes and rejections, and how to prevent a repeating workflow from extending one chain indefinitely.
Related concepts
- promiseused by · A JavaScript Promise is an object representing the eventual completion or failure of an asynchronous operation and its resulting value or reason.
- memory leakaddresses · A memory leak is the unintended retention of allocated memory that a program no longer needs, preventing that memory from being reclaimed for reuse.
- compositionequivalent to · Composition is a technique for combining simpler functions, components, or operations into a larger structure or behavior.
- then methoduses · The JavaScript Promise then method registers fulfillment and rejection handlers and returns a new promise that represents their results.
- Promise#catchuses · Promise#catch is a JavaScript Promise method that registers a handler for rejection and returns a Promise for the handler's outcome.
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