How to use the mapLimit function from async

async.mapLimit is a JavaScript function that applies an asynchronous function to each element of an array with a specified concurrency limit.

How does async.mapLimit work?

async.mapLimit works by processing an array of values in parallel with a specified concurrency limit, applying an asynchronous function to each element of the array. The function takes three arguments: the array of values to be processed, the maximum number of concurrent operations to allow, and the asynchronous function to apply to each element of the array. The asynchronous function is called with two arguments: the current element of the array and a callback function to be called when the asynchronous operation is complete. The callback function takes two arguments: an error object (if an error occurred during the asynchronous operation) and the result of the operation. async.mapLimit returns a Promise that resolves to an array of the results of each asynchronous operation. By limiting the number of concurrent operations, async.mapLimit provides a way to process large arrays of data without overwhelming the system or exceeding resource limits. This makes it useful for a variety of tasks, such as making multiple API requests in parallel or processing large datasets asynchronously.

Ai Example

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const async = require("async");
const request = require("request");

// An array of URLs to fetch
const urls = [
  "https://www.example.com",
  "https://www.google.com",
  "https://www.github.com",
  "https://www.twitter.com",
  "https://www.linkedin.com",
];

// A function to fetch a URL and return its contents
function fetchUrl(url, callback) {
  request(url, (err, response, body) => {
    if (err) {
      return callback(err);
    }
    callback(null, body);
  });
}

// Use async.mapLimit to fetch the URLs with a concurrency limit of 3
async.mapLimit(urls, 3, fetchUrl, (err, results) => {
  if (err) {
    return console.error(err);
  }
  console.log(results);
});

In this example, we use async.mapLimit to fetch the contents of several URLs in parallel, limiting the number of concurrent requests to 3. We first define an array of URLs to fetch and a function to fetch each URL using the request module. We then use async.mapLimit to apply the fetchUrl function to each URL in the urls array, limiting the number of concurrent operations to 3. Finally, we log the results of each asynchronous operation to the console. By using async.mapLimit, we can efficiently process large arrays of data in parallel, without overwhelming the system or exceeding resource limits.