The YUI Global Object includes several useful type-checking methods in the Lang
object.  In addition to the 'isXYZ' type check methods, YUI 3 includes
Y.Lang.type, which returns a string representing the type of the tested
object.  Click the "Check" button in each row to evaluate the data.
| Data | isObject | isArray | isFunction | type | 
|---|---|---|---|---|
| null | ||||
| [] or new Array() | ||||
| {} or new Object() | ||||
| function Foo() {} | ||||
| new Foo() | ||||
Type Checking with YUI
YUI().use('node', function(Y) {
    // This method is in the core of the library, so we don't have to use() any
    // additional modules to access it.  However, this example requires 'node'.
Checking types
In this example, we use a few of the type-checking methods available in
Lang to test various types of data.
// Test the input using Y.Lang type checking methods
var checkType = function (val) {
    return {
        'object'  : Y.Lang.isObject(val),
        'array'   : Y.Lang.isArray(val),
        'function': Y.Lang.isFunction(val),
        'type'    : Y.Lang.type(val)
    };
};
Full Source
YUI().use('node', function(Y) {
    // This method is in the core of the library, so we don't have to use() any
    // additional modules to access it.  However, this example requires 'node'.
    var checkType = function (val) {
        return {
            'object'  : Y.Lang.isObject(val),
            'array'   : Y.Lang.isArray(val),
            'function': Y.Lang.isFunction(val),
            'type'    : Y.Lang.type(val)
        };
    };
    var populateRow = function (e, data) {
        var target = e.target;
            cell = target.get('parentNode'),
            row  = cell.get('parentNode');
        row.removeChild(cell);
        var td0 = document.createElement('td'),
            td1 = td0.cloneNode(false),
            td2 = td0.cloneNode(false);
            td3 = td0.cloneNode(false);
        var results = checkType(data);
        td0.appendChild(document.createTextNode(results['object']   ? 'Y' : 'N'));
        td1.appendChild(document.createTextNode(results['array']    ? 'Y' : 'N'));
        td2.appendChild(document.createTextNode(results['function'] ? 'Y' : 'N'));
        td3.appendChild(document.createTextNode(results['type']));
        row.appendChild(td0);
        row.appendChild(td1);
        row.appendChild(td2);
        row.appendChild(td3);
    };
    var foo = function () {};
    var f = Y.one('#demo');
    Y.on('click',populateRow, '#demo-1', Y, null);
    Y.on('click',populateRow, '#demo-2', Y, []);
    Y.on('click',populateRow, '#demo-3', Y, {});
    Y.on('click',populateRow, '#demo-4', Y, foo);
    Y.on('click',populateRow, '#demo-5', Y, new foo());
});