vEnqueuer

An javascript asynchronous code enqueuer. Perfect for queue up repetitive i/o tasks that should be executed in order, in a way that the end of one task calls the next in the queue, all this asynchronously, of course. You just need to register the function which you want queue up and call vEnqueuer's methods like enqueue or trigger.

Install vEnqueuer

npm install venqueuer --save

How to use

    var vEnqueuer = require('venqueuer');
    var venqueuer = new vEnqueuer();
  

Creating a queue

With vEnqueuer, it's possible to create multiple queues, each one responsible for managing specific tasks. For instance, we can create a 'download' queue, and a 'unzip' queue. In the download's queue we want to queue up just download tasks, and we'd like to call unzip tasks just after all downloads have been completed. The code below does just that:

    venqueuer.createQueue("unzip", function(){
  		console.log("all files unzipped!");
  	});
  	
  	venqueuer.createQueue("download", function(){
	        console.log("all downloads have been completed!");
        vEnqueuer.trigger("unzip");
    });	
    

By now, we have just created queues and set callback functions to them. These callback functions tells the queue what to do when all its tasks are completed. Let's say we want to download 3 files in a predefined order:

    downloadLinks.forEach(function(l){
        venqueuer.enqueue("download", downloadFn, { //downloadFn is a reference to download's function
            
            url: l,  //url is an argument required by the downloadFn
            dest: './folder', //dest is an argument required by the downloadFn
            
            //callback is the callback which will be used by downloadFn when download completes
            callback: function(err){  //an error argument is passed in case of error during download
              if(err){
                console.log("an error occurred", err);
                return;
              }
              console.log("successful download");
              
              //some code to enqueue unzip task...
              
            }
            
        });
        
        if( isLastIteration() ){
            //initiate queued tasks when the list has been traversed
            venqueuer.trigger("download");
            
        }
        
    });
    

From now, you may understand vEnqueuer and is fully capable of complete the //some code to enqueue unzip task.

This binding

Bind a 'this' object to the task function its really simple, you just need to pass the 'this' object as an extra attribute called self in your literal object:

    venqueuer.enqueue("download", downloadFn, { 
          self:someObject, 
          url: l, 
          dest: './folder', 
          callback: function(err){...}
    });