Can You Spot the Subtle Differences in These Four Promise Patterns?

At the end of 2016, almost every JavaScript developer had already learned to use Promises in daily development.

However, not everyone truly understands some details of Promises. Below are four Promise use cases—can you tell the differences?

doSomething().then(v => doSomethingElse(v)).then(finalHandler);

doSomething().then(function(v) {
  doSomethingElse(v);
}).then(finalHandler);

doSomething().then(doSomethingElse()).then(finalHandler);

doSomething().then(doSomethingElse).then(finalHandler);

I bet fewer than half can point out the exact distinctions.

Only curious programmers make progress, so if you’re reading this on your phone, are you eager to click “Read the original article” to find out?

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