Chaining Async Await with loop

Question

I have 2 functions with loops that I want to execute sequentially:

Function A executes
Within Function A there is a For loop triggering an external function
Once loop in Function A is finished doing its thing, then we start with Function B

I have tried with the following code but function B starts in parallel, doesn't wait for Function A to finish:

async function sendPosts() {
    console.log("start send posts")
    for (let post of posts) {
        ...
  
        await channel.send({
            ...
        }).then((message) => {
            externalFunction(message);
        })
        .catch(err => console.log(err));
    }
    console.log("finish send posts")    
}

async function sendComments() {
    console.log("start send comments")
    for (let comment of commentsData) {
        ... 
    }
    console.log("finish send comments")
}   

sendPosts().then(sendComments());

`sendComments()` executes the function and assigns its return value as the resolve handler of `sendPosts()`. Just remove the `()` — Andreas, Feb 02 '22 at 09:20
`sendPosts` don't return `Promise` - then why you chainging like `Promise` `sendPosts().then(sendComments());` or I am blind?? — zbyso, Feb 02 '22 at 09:43
@Andreas want to put this as answer and ill mark it as correct? — Eric Mitjans, Feb 02 '22 at 09:44
Nope. I voted to close as typo (because I can never find the duplicate for this type of problem... :/). — Andreas, Feb 02 '22 at 09:49
@zbyso [Async function returning promise, instead of value](https://stackoverflow.com/q/51338277) | [async/await implicitly returns promise?](https://stackoverflow.com/q/35302431) | [Why is my asynchronous function returning Promise { } instead of a value?](https://stackoverflow.com/q/38884522) — VLAZ, Feb 02 '22 at 12:53
`sendPosts().then(sendComments());` -> `sendPosts().then(() => sendComments());` or `sendPosts().then(sendComments);` see [What is the difference between a function call and function reference?](https://stackoverflow.com/q/15886272) | [addEventListener calls the function without me even asking it to](https://stackoverflow.com/q/16310423) | [In JavaScript, does it make a difference if I call a function with parentheses?](https://stackoverflow.com/q/3246928) — VLAZ, Feb 02 '22 at 12:55
@VLAZ @Noam thanks, I don't know this: "If you don't explicitly return a promise, the value you return will automatically be wrapped in a promise.", I do manually `return new Promise...` every time :) — zbyso, Feb 02 '22 at 13:55

score -1 · Answer 1 · answered Feb 02 '22 at 10:37

-1

For of loop is not awaited. you looking for something as following

    for await (const variable of iterable)

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for-await...of

Foreach loop has acting the same

answered Feb 02 '22 at 10:37

Alantod17

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Chaining Async Await with loop

1 Answers1