one-concurrent

Allows you to 'call' an asynchronous function multiple times, each time with a callback supplied, but only ever have one instance of the function running concurrently

Install

1$ npm install --save one-concurrent

Usage

1var oneConcurrent = require("one-concurrent");
2
3oneConcurrent(function (callback) {
4	// Call your long-running function here, passing it the provided callback variable
5	longRunningTask(callback);
6
7}, function (something) {
8
9	// This is your actual callback. (In this case, called by 'longRunningTask')
10})

• func Function - An anonymous function with a single callback param, which -inside- calls your real function. Example: function (callback) { longRunningTask(callback); }
• callback Function - Callback to call

Example

1var oneConcurrent = require("one-concurrent");
2
3function longRunningTask(callback) {
4	
5	console.log(`Doing long-running stuff…`);
6
7	setTimeout(function () { // Simulate long-running task
8		callback(Math.random()); // Return a random number
9	}, 1*1000);
10} 
11
12function runTasks() {
13
14	oneConcurrent(function (callback) {
15		longRunningTask(callback);
16
17	}, function (randomNumber) {
18
19		console.log(`Got random number: ${randomNumber}`);
20	})
21}
22
23runTasks();
24runTasks();
25runTasks();
26
27setTimeout(runTasks, 3*1000); // Run again in 3 seconds
28
29//=> Doing long-running stuff…
30//=> Got random number: 0.15694928092347604
31//=> Got random number: 0.15694928092347604
32//=> Got random number: 0.15694928092347604
33//=> Doing long-running stuff…
34//=> Got random number: 0.9069438411363342