Created
June 11, 2013 16:24
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Promises doodle
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function retProm() { | |
var def = when.defer(); | |
return def.resolve(); | |
} | |
console.log('one'); | |
retProm().then(function(){console.log('two')); | |
console.log('three'); | |
// this will print: | |
// | |
// one | |
// three | |
// two |
No, this could print Z, Y, X. There is no requirement that X come before Y. The spec is still following as long as Y comes after Z.
Let me explain further the difference between our two examples. In yours, when you call def.resolve
, then
has not yet returned. So the implementation must insert an extra tick before calling onFulfilled
, to ensure that then
returns first.
In my example, when I call def.resolve
, then
has already returned, since an async operation has already happened. So the implementation does not have to insert an extra tick before calling onFulfilled
, since then
has already returned.
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Using your example excluding the nextTick:
This will print: Z, X, Y
If there was no extraTick in the promise implementation for resolving the promise, it would be: Z, Y, X