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# Example: Check Data Types with `Lang`

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());

    });