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Author SHA1 Message Date
xfarrow
7b10c3ce19 Update 3_async-await.js 2025-01-08 15:14:46 +01:00
xfarrow
04ab3177d2
Update 3_async-await.js 2025-01-08 13:01:01 +01:00
1 changed files with 50 additions and 10 deletions
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asynchronous_programming/3_async-await.js
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@ -23,14 +23,13 @@ async function f2 () {
f2()
// The code in the same function after "await"
// is to be intended in the "then()" of the primise. This means
// that after await (but before the completion of the Promise),
// the flow of execution goes out that code block. For example
// consider the following example:
// is to be intended in the "then()" of the promise.
// Consider the following example:
async function exampleAsyncFunction () {
console.log('Before await')
await new Promise(function (resolve, reject) {
setTimeout(() => resolve('done'), 500)
console.log("In the Promise")
setTimeout(() => resolve(), 500)
}) // Pauses execution here until the promise resolves.
console.log('After await')
}
@ -38,11 +37,52 @@ console.log('Start')
exampleAsyncFunction()
console.log('End')
// The result will be:
// Start, Before Await, End, After await
// "End" comes before "After Await" because the
// flow of execution goes to the caller
// when await is invoked.
/*
The result will be:
Start, Before Await, In the Promise, End, After await
"End" comes before "After Await" because the
flow of execution goes to the caller of exampleAsyncFunction
after setTimeout() gets enqueued in the Event Loop Thread
but before 500ms have elapsed.
+---------------+
| Main |
+---------------+
|
|
v
+----------------------+
|exampleAsyncFunction |
+----------------------+
|
|
v
+---------------+
| Promise |
+---------------+
|
|
v
+----------------------------------------+
|Enqueue resolve() and exit immediately | +--------------------------------+
+----------------------------------------+ -------------------------------> |Wait 500ms in the libuv library |
| +--------------------------------+
| Nothing left to do in the AWAIT, return to caller |
v |
+---------------+ |
| Main | |
+---------------+ |
| |
| |
v |
+-------------------+ |
| Then() of Promise | <-----------------------------------------------------------
+-------------------+
*/
// Questions
//