Few things which I learned

I just want to write few things which I learned these days.

$.Callbacks - sort of a queue of functions, where all be executed at once on fire. Example:

function consoleLogtestOne() {
    console.log("test one")
}

function consoleLogtestTwo() {
    console.log("test two")
}

var myCallbacks = $.Callbacks();

myCallbacks.add(consoleLogtestOne);
myCallbacks.add(consoleLogtestTwo);
myCallbacks.fire();

With line of code:

myCallbacks.fire();

we are executing both functions at once.

Array.prototype.map(Function) - executes callback function for each member in array. Example:

/*global console*/
(function () {
    "use strict";
    var myNumbers = [1, 4, 9],
        variableWhichWillDoNothing;
    variableWhichWillDoNothing = myNumbers.map(function (currentValue, index, array) {
        console.log("currentValue: " + currentValue);
        console.log("index: " + index);
        console.log("array: " + array);
        console.log("---");
        return "nothing";
    });
    console.log("Just to do something with doubles (to satisfy jsLint): " + variableWhichWillDoNothing);
}())

Result will be something like:

Function.prototype.apply() - provides arguments as array to function.

Check these two examples:

function applyLog() {
    console.log.apply(console, arguments);
}

function justLog() {
    console.log(arguments);
}

If you execute justLog like this:

justLog("test1", "test2")

Result will something like this:

As you can see result is an array.

Now lets execute applyLog:

applyLog("test1", "test2")

Result is something like:

As you can see no array.

Using apply and map you can generate array of elements, for example:

Array.apply(null, Array(24)).map(function (_, i) {return ('0' + i)});

Result:

["00", "01", "02", "03", "04", "05", "06", "07", "08", "09", "010", "011", "012", "013", "014", "015", "016", "017", "018", "019", "020", "021", "022", "023"]

slice - select elememts

Check this example:

('stanko').slice(-1)

Result:

"o"

Another:

('stanko').slice(-2)

Result:

"ko"

One more:

('stanko').slice(2)

Result:

"anko"