Core contains an handful of common sense functions used in MooTools. It also contains some basic Hash and Array methods.

Checks to see if a value exists or is 0. Useful for allowing 0.

$chk(item);

1. item - (mixed) The item to inspect.

• (boolean) If the object passed in exists or is 0, returns true. Otherwise, returns false.

function myFunction(arg){
    if($chk(arg)) alert('The object exists or is 0.');
    else alert('The object is either null, undefined, false, or ""');
}

Clears a Timeout or an Interval. Useful when working with Function:delay and Function:periodical.

$clear(timer);

1. timer - (number) The identifier of the setInterval (periodical) or setTimeout (delay) to clear.

• (null) returns null.

var myTimer = myFunction.delay(5000); //Waits 5 seconds then executes myFunction.
myTimer = $clear(myTimer); //Cancels myFunction.

• Function:delay
• Function:periodical

Checks to see if a value is defined.

$defined(obj);

1. obj - (mixed) The object to inspect.

• (boolean) If the object passed is not null or undefined, returns true. Otherwise, returns false.

function myFunction(arg){
    if($defined(arg)) alert('The object is defined.');
    else alert('The object is null or undefined.');
}

Creates a function which returns the passed argument according to the index (i) passed.

var argument = $arguments(i);

1. i - (number) The index of the argument to return.

• (function) The function that returns a certain argument from the function's arguments.

var secondArgument = $arguments(1);
alert(secondArgument('a','b','c')); //Alerts "b".

An empty function, that's it. Typically used for as a placeholder inside event methods of classes.

var emptyFn = $empty;

var myFunc = $empty;

Creates an empty function which does nothing but return the value passed.

var returnTrue = $lambda(true);

1. value - (mixed) The value for the created function to return.

• (function) A function which returns the desired value.

myLink.addEvent('click', $lambda(false)); //Prevents a link Element from being clickable.

Copies all the properties from the second object passed in to the first object passed in.

$extend(original, extension);

1. original - (object) The object to be extended.
2. extension - (object) The object whose properties will be copied to original.

• (object) The first object passed in, extended.

var firstObj = {
    'name': 'John',
    'lastName': 'Doe'
};
var secondObj = {
    'age': '20',
    'sex': 'male',
    'lastName': 'Dorian'
};
$extend(firstObj, secondObj);
//firstObj is now: {'name': 'John', 'lastName': 'Dorian', 'age': '20', 'sex': 'male'};

Merges any number of objects recursively without referencing them or their sub-objects.

var merged = $merge(obj1, obj2[, obj3[, ...]]);

1. (objects) Any number of objects.

• (object) The object that is created as a result of merging all the objects passed in.

var obj1 = {a: 0, b: 1};
var obj2 = {c: 2, d: 3};
var obj3 = {a: 4, d: 5};
var merged = $merge(obj1, obj2, obj3); //returns {a: 4, b: 1, c: 2, d: 5}, (obj1, obj2, and obj3 are unaltered)

var nestedObj1 = {a: {b: 1, c: 1}};
var nestedObj2 = {a: {b: 2}};
var nested = $merge(nestedObj1, nestedObj2); //returns: {a: {b: 2, c: 1}}

Used to iterate through iterables that are not regular arrays, such as built in getElementsByTagName calls, arguments of a function, or an object.

$each(iterable, fn[, bind]);

1. iterable - (object or array) The object or array to iterate through.
2. fn - (function) The function to test for each element.
3. bind - (object, optional) The object to use as 'this' within the function. For more information see Function:bind.

fn(item, index, object)

1. item - (mixed) The current item in the array.
2. index - (number) The current item's index in the array. In the case of an object, it is passed the key of that item rather than the index.
3. object - (mixed) The actual array/object.

$each(['Sun','Mon','Tue'], function(day, index){
    alert('name:' + day + ', index: ' + index);
}); //Alerts "name: Sun, index: 0", "name: Mon, index: 1", etc.

//Alerts "The first day of the week is Sunday", "The second day of the week is Monday", etc:
$each({first: "Sunday", second: "Monday", third: "Tuesday"}, function(value, key){
    alert("The " + key + " day of the week is " + value);
});

Returns the first defined argument passed in, or null.

var picked = $pick(var1[, var2[, var3[, ...]]]);

• (mixed) Any number of variables.

• (mixed) The first variable that is defined.
• (null) If all variables passed in are null or undefined, returns null.

function say(infoMessage, errorMessage){
    alert($pick(errorMessage, infoMessage, 'There was no message supplied.'));
}
say(); //Alerts "There was no message supplied."
say("This is an info message."); //Alerts "This is an info message."
say("This message will be ignored.", "This is the error message."); //Alerts "This is the error message."

Returns a random integer between the two passed in values.

var random = $random(min, max);

1. min - (number) The minimum value (inclusive).
2. max - (number) The maximum value (inclusive).

• (number) A random number between min and max.

alert($random(5, 20)); //Alerts a random number between 5 and 20.

Converts the argument passed in to an array if it is defined and not already an array.

var splatted = $splat(obj);

1. obj - (mixed) Any type of variable.

• (array) If the variable passed in is an array, returns the array. Otherwise, returns an array with the only element being the variable passed in.

$splat('hello'); //Returns ['hello'].
$splat(['a', 'b', 'c']); //Returns ['a', 'b', 'c'].

Returns the current time as a timestamp.

var time = $time();

• (number) - The current timestamp.

Tries to execute a number of functions. Returns immediately the return value of the first non-failed function without executing successive functions, or null.

$try(fn[, fn, fn, fn, ...]);

• fn - (function) The function to execute.

• (mixed) Standard return of the called function.
• (null) null if all the passed functions fail.

var result = $try(function(){
    return some.made.up.object;
}, function(){
    return jibberish.that.doesnt.exists;
}, function(){
    return false;
});

//result is false

var failure, success;

$try(function(){
    some.made.up.object = 'something';
    success = true;
}, function(){
    failure = true;
});

if (success) alert('yey!');

Returns the type of object that matches the element passed in.

$type(obj);

1. obj - (object) The object to inspect.

• 'element' - (string) If object is a DOM element node.
• 'textnode' - (string) If object is a DOM text node.
• 'whitespace' - (string) If object is a DOM whitespace node.
• 'arguments' - (string) If object is an arguments object.
• 'array' - (string) If object is an array.
• 'object' - (string) If object is an object.
• 'string' - (string) If object is a string.
• 'number' - (string) If object is a number.
• 'date' - (string) If object is a date.
• 'boolean' - (string) If object is a boolean.
• 'function' - (string) If object is a function.
• 'regexp' - (string) If object is a regular expression.
• 'class' - (string) If object is a Class (created with new Class, or the extend of another class).
• 'collection' - (string) If object is a native htmlelements collection, such as childNodes, getElementsByTagName, etc.
• 'window' - (string) If object is the window object.
• 'document' - (string) If object is the document object.
• 'event' - (string) If object is an event.
• false - (boolean) If object is undefined, null, NaN or none of the above.

var myString = 'hello';
$type(myString); //Returns "string".