Nodejs: How to write high performance async loop

Question

have a initUrl, its an article which contains next blog, and defind function getNextUrl(url, callback(err, nextUrl)), want to get the next 100th url.

In stormjs (developing https://github.com/guileen/stormjs/issues/1), it write as

var url = initUrl;
for(var i=0; i<100; i++){
  url = getNextUrl(url, _);
}
console.log(url);

but what the best output should be, I want to know how noders write this code without 3rd module.

Won't the above code be automatically synchronous irrespective of whether you're calling async functions and callbacks or not? — Denis de Bernardy
– Denis de Bernardy, Commented May 20, 2011 at 8:37
@Denis he's using an async shorthand _ is some kind of magic flow control thing. — Raynos
– Raynos, Commented May 20, 2011 at 8:38

Raynos · Accepted Answer · 2011-05-20 09:54:01Z

3

arr = [];
(function recurse(url, i) {
    getNextUrl(url, function(err, nextUrl) {
        if (!err) {
            arr.push(nextUrl);
            if (i < 100) recurse(nextUrl, i++);
        }
    });
}("", 0);

I call this pattern boot strapped recursion.

If you prefer it to be more concise rather then efficient you can use some .bind magic.

(function recurse(i, err, url) {
    if (!err) arr.push(url);

    if (i < 100) getNextUrl(url, recurse.bind(null, ++i));
}(0, "trick it", url);

edited May 20, 2011 at 9:54

answered May 20, 2011 at 8:42

Raynos

170k57 gold badges359 silver badges399 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

guilin 桂林 Over a year ago

Can I drop the 3rd arguments urlarr

Raynos Over a year ago

@guilin yes if you want to make it global.

Collectives™ on Stack Overflow

Nodejs: How to write high performance async loop

1 Answer 1

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related