slooooooow

gistfile1.js

asyncMap = function(fn, list, callback){
    var counter = 0;
    var result = list.slice();
    list.forEach(function(elem, index){
        setTimeout(function(){
            if(++counter === result.length){
                callback(result);
            }
            result[index] = fn(elem);
        },
        0)
    });
}

syncMap = function(fn, list, callback){
    var result = [];
    list.forEach(function(elem){
        result.push(fn(elem));
    });
    callback(result);
}

time = function(f){
    var res = [];
    for(var i = 0; i < 1000000; i++){
        res.push(i);
    }
    asyncstart = new Date();
    asyncMap(function(a){return f(a)}, res, function(){console.log('asyncMap ran in ' + (new Date() - asyncstart) + ' milliseconds')})
    syncstart = new Date();
    syncMap(function(a){return f(a)}, res, function(){console.log('syncMap ran in ' + (new Date() - syncstart) + ' milliseconds')})
}

time(function(a){return a + 1});