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Promise: chaining then()

Chaining promises can enhance readability of asynchronous code.

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chaining multiple promises can enhance readability

prerequisites for understanding

  • reminder: the test passes when a fulfilled promise is returned
  • a function given to then() fulfills (if it doesnt throw)

chain promises

  • then() receives the result of the promise it was called on
  • multiple then()s can be chained
  • order of the then()s matters
  • any of the things given to then() can resolve asynchronously (the real power of Promises)
  • also asynchronously, the order still matters, promises wait, but don`t block


The description of how a value given to `then()` becomes a resolved promise.
Looks like the description in the spec of what `then()` accepts and does with the given value.
A long article introducing promises.