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Here is one more example of a synchronous question, but a little bit more advanced, as you can see

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here, we have a question execute the given list of asynchronous functions in parallel and return.

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The result is in the race to the callback.

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As you can see here, we already have three functions and this is given with the task.

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So each function have here inside the callback, which returns one, two and three.

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Most important, but here that first function is three seconds, then two seconds, then one second.

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And then we must write the function async parallel where inside were throwing an array of asynchronous

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functions, which means every single function has a callback.

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Enter the second parameter we have here own callback for a single parallel.

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Here we are getting our result and we are console.log in it here and we must get in this case, one

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two three because it must print results or feature asynchronous function in order, which actually means

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where execute executing three functions in parallel, and we're waiting for all of them to complete.

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And after this, we have the correct order of the results, which actually means we are getting results

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of every single function and actually we're using parallel fetch and, for example, quite a lot every

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day because we want, for example, to fetch three different requests simultaneously and then get all

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data in one place and merge it somehow.

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This is why let's build dysfunctional, but it's not easy, and we really need to think what we are

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doing here.

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So we want to implement a sink parallel function and actually here we get getting first of all and a

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ray of asynchronous functions so we can right here, I think thanks.

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And the second parameter is our callback.

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And importantly, this is a callback for a sink parallel, not for the specific async func function.

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And first of all, here I want to create an array variable, put our results.

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So here I can write a result array.

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And here we want to write new array and inside async functions dot length.

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In this case, we are preparing the empty array with three elements.

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And obviously it is three only for our case, and it can be any length of our asynchronous functions.

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After this, I want to create a result counter and by default it will be zero until the length of our

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array.

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Why do we need that?

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Because actually every single asynchronous function can be ended in random time, and we must wait for

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all this function to complete.

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This means that we must count how many functions are already completed until we are rich in length.

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This is why here let's create our result.

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Count them, and by default, it will be zero.

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And now we want to look through our asynchronous functions.

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So here are some funnels dot for each and really using follow up here and we get an access for every

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single asynchronous function.

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And we also need here an index because we need to store the results also in the same correct order.

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Now inside for each, we must call our asynchronous function.

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Most importantly, we don't know at all what this function is doing, but we know that this function

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gets a callback.

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This is why here we can write our callback.

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So we're calling a single function without any arguments.

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And inside were providing our comic if this callback is triggered.

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This means that we are ready with our asynchronous function and now we want to write the result inside

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our brain.

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This is where here actually, we're getting in our callback value.

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And as you can see here, inside every single callback, we're getting a value.

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And this is exactly the value that we're getting inside our callback here.

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Number one to store this value inside our result today.

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So here we can write results, right?

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And here will be our index equals value.

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And just to remind you, whichever index here, this is why we know that was stored it correctly.

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For example, this is the third function and it will be triggered first.

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Then we will write it on the index.

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After this, we must increase our result counter to know that one of the functions is done.

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And last but not least, we want to check if this function was the last one.

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So here we can check if our result counter bigger or equal async function.

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Then we want to call our callback for a single parallel.

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So here we can simply write, callback and inside were provided our result array.

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So once again, what we are doing here?

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First of all, we are preparing an empty array and our content.

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Well, looping through our asynchronous functions and we're calling every single function.

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And here we are, providing in every function, a callback.

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And when we're getting success with, first of all, store our result in result index.

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And then we increase our content.

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In this case, we know that this logic will return us callback for a simple parallel when we're ready

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and when all our functions are completed.

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So here we are, calling our callback with results right now.

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Actually, we must move this function before our call async parallel because we must write it in Wisconsin

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and let's check if it's working.

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I'm relied in the page and we're getting an error assignment to constant variable.

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Let's check the result.

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Yes, as you can see, the result counter can be increased because it is const.

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So here we can write led and then it should work.

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Let's check the sound.

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I'm reloading the page with don't have any errors.

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Now, three seconds passed and we're getting our array was one to three, which actually means here

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are a sync.

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Parallel waits for every single asynchronous function to be completed.

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And then we generate as a callback our result here and now we can use our array in the correct order.

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And this is completely fine if you can build this function fast.

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Most importantly, if you are doing it in the interview, you must always say out loud what you are

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doing and how you are thinking, because normally on the interview, it's not that important.

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If you solve this task fully or not, you must show your way of thinking and how you want to solve this

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specific task.