_______  _        _______  ______            _______  _        _______ 
                  (  ___  )( (    /|(  ____ \(  ___ \ |\     /|(  ___  )( (    /|(  ____ \
                  | (   ) ||  \  ( || (    \/| (   ) )( \   / )| (   ) ||  \  ( || (    \/
                  | |   | ||   \ | || (__    | (__/ /  \ (_) / | |   | ||   \ | || (__    
                  | |   | || (\ \) ||  __)   |  __ (    \   /  | |   | || (\ \) ||  __)   
                  | |   | || | \   || (      | (  \ \    ) (   | |   | || | \   || (      
                  | (___) || )  \  || (____/\| )___) )   | |   | (___) || )  \  || (____/\
                  (_______)|/    )_)(_______/|/ \___/    \_/   (_______)|/    )_)(_______/
                                                                                          

onebyone - Flow control so that only one function executes at any one time.

Like async.series() but you can keep adding functions to it.

Gives you an object (like a queue) into which you can add functions and each will only ever run in series, never concurrently, and only one at a time. Also gives you your result immediately, rather than at the end of the series.

var onebyone = require('onebyone')();

var one = function(callback) {
    setTimeout(function() {
        callback(null, 'Ok');
    }, 2000);
};

var two = function(callback) {
    setTimeout(function() {
        callback(null, 'Ok');
    }, 1000);
};

console.log('Setting up tasks : ' + (new Date()).toISOString());
onebyone.add(one, function(err, data) {
    console.log('One has finished : ' + (new Date()).toISOString());
});
onebyone.add(two, function(err, data) {
    console.log('Two has finished : ' + (new Date()).toISOString());
});

Will give an output similar to the following:

Setting up tasks : 2012-06-05T05:33:25.549Z
One has finished : 2012-06-05T05:33:27.561Z
Two has finished : 2012-06-05T05:33:28.563Z

Written by: Andrew Chilton - Blog - Twitter.

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