# 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, YUI3 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()` |