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javascript async queue

Lucky Yoila answered on February 5, 2023 Popularity 7/10 Helpfulness 2/10

answer javascript async queue

related async queue

javascript async queue

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function createQueue(tasks, maxNumOfWorkers = 4) {
  var numOfWorkers = 0;
  var taskIndex = 0;

  return new Promise(done => {
    const handleResult = index => result => {
      tasks[index] = result;
      numOfWorkers--;
      getNextTask();
    };
    const getNextTask = () => {
      if (numOfWorkers < maxNumOfWorkers && taskIndex < tasks.length) {
        tasks[taskIndex]().then(handleResult(taskIndex)).catch(handleResult(taskIndex));
        taskIndex++;
        numOfWorkers++;
        getNextTask();
      } else if (numOfWorkers === 0 && taskIndex === tasks.length) {
        done(tasks);
      }
    };
    getNextTask();
  });
}

Popularity 7/10 Helpfulness 2/10 Language javascript

Source: krasimirtsonev.com

Tags: javascript queue

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Contributed on Sep 13 2023

Lucky Yoila

0 Answers Avg Quality 2/10

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async queue

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using a sync queue to throttle requests

// Including the async module
const async = require('async');

// Creating an array for all elements execution
const tasks = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

// Initializing the queue
const queue = async.queue((task, executed) => {
   console.log("Currently Busy Processing Task " + task);

   setTimeout(()=>{
      // Number of tasks remaining and to be processed
      const tasksRemaining = queue.length();
      executed(null, {task, tasksRemaining});
   }, 1000);

}, 1); // concurrency value = 1

// Queue is idle initially as no elements are there...
console.log(`Queue Started ? ${queue.started}`)

// Adding each task from the tasks list
tasks.forEach((task)=>{

   // Adding the task 5 to the head for priority execution
   if(task == 5){
      queue.unshift(task, (error, {task, tasksRemaining})=>{
         if(error){
            console.log(`An error occurred while processing task ${task}`);
         }else {
            console.log(`Finished processing task ${task}. ${tasksRemaining} tasks remaining`);
         }
      })
      // Adding all the tasks at tail to be executed except task 5
   } else {
      queue.push(task, (error, {task, tasksRemaining})=>{
         if(error){
            console.log(`An error occurred while processing task ${task}`);
         }else {
            console.log(`Finished processing task ${task}. ${tasksRemaining}
            tasks remaining`);
         }
      })
   }
});

// Executes the callback when the queue is done processing all the tasks
queue.drain(() => {
   console.log('All items are succesfully processed !');
})

// Checking if the queue is started after adding tasks
console.log(`Queue Started ? ${queue.started}`)

/*
console.log(queue.length());

// Executes when the queue is done processing all the items
queue.drain(() => {
    console.log('Successfully processed all items');
})

// Pauses the execution of the queue
queue.pause()

// Resumes the execution of the queue
queue.resume()

// Forces the queue into idle mode
// and removes the drain callback
queue.kill()

// Returns whether the queue is idle or not
queue.idle()

Queue Started ? False
Queue Started ? True
Currently Busy Processing Task 5
Finished processing task 5. 9 tasks remaining
Currently Busy Processing Task 1
Finished processing task 1. 8 tasks remaining
Currently Busy Processing Task 2
Finished processing task 2. 7 tasks remaining
Currently Busy Processing Task 3
Finished processing task 3. 6 tasks remaining
Currently Busy Processing Task 4
Finished processing task 4. 5 tasks remaining
Currently Busy Processing Task 6
Finished processing task 6. 4 tasks remaining
Currently Busy Processing Task 7
Finished processing task 7. 3 tasks remaining
Currently Busy Processing Task 8
Finished processing task 8. 2 tasks remaining
Currently Busy Processing Task 9
Finished processing task 9. 1 tasks remaining
Currently Busy Processing Task 10
Finished processing task 10. 0 tasks remaining
All items are succesfully processed !
*/

Popularity 9/10 Helpfulness 3/10 Language javascript

Source: www.tutorialspoint.com

Tags: queue javascript

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Contributed on Feb 05 2023

Muddy Mandrill

0 Answers Avg Quality 2/10

javascript async queue

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