CODEWITHSUNDEEP
javascriptnode.jsasynchronouspushshift
Alexanus
Alexanus

Reputation: 689

js asynchronously using array push() shift()

I have two intervals that need access to the same data. So in one interval I want to push() an element to an array and then in the other interval I want to get the first element from the array and then remove it.

for example:

let array = [];
let count = 0;

setInterval( () => {
    array.push(count);
    count++;
}, 1000);

setInterval( () => {
    let data = array[0];
    array.shift();
    console.log("received data: "+data);
}, 1000);

the output of this is:

received data: 0
received data: 1
received data: 2
received data: 3
....

Does this also work with more complex functions and bigger arrays? Could this cause any weird behaviour? Maybe it could shift and push at the same time and mess up the array? Is this a good way to do that? Are there better ways?

EDIT:
The reason i want to do this. Is because I want to download data from many different links. So inside my script i call a download(link) function, but this will result in the script trying to download a lot of links at the same time. So i want to create a buffer, so that the script only downloads from 100 links at the same time.
Inside the script i want to call download(link) wherever i want and then let an interval take care of downloading only 100 links at the same time. So it removes 100 links from a buffer and downloads them. While the script pushes new links to the same array.

My main concern is that while i am doing a shift() the array will reorganize itself somehow. Might js try to make a push() in between this reorganization phase? Or will js not do any array operations on the array until shift() is completed?

Upvotes: 0

Views: 1466

Answers (1)

CertainPerformance
CertainPerformance

Reputation: 371049

Your general idea of pushing links to an array asynchronously and then removing them from the array in a separate asynchronous task is fine, it'll work.

My main concern is that while i am doing a shift() the array will reorganize itself somehow. Might js try to make a push() in between this reorganization phase? Or will js not do any array operations on the array until shift() is completed?

Javascript is single-threaded, so this isn't something to worry about - if one interval triggers a function that does stuff, that function's synchronous actions (like manipulating an array) will run to the end before any other interval callbacks can run.

The issue of shared mutable state is a problem for many other languages, but not for Javascript, at least in most cases.

Upvotes: 3

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