Get document hight and width from javascript

Using this functions can get document hight and width

function GetHeight()
{
        var y = 0;
        if (self.innerHeight)
        {
                y = self.innerHeight;
        }
        else if (document.documentElement && document.documentElement.clientHeight)
        {
                y = document.documentElement.clientHeight;
        }
        else if (document.body)
        {
                y = document.body.clientHeight;
        }
        return y;
}


function GetWidth()
{
        var x = 0;
        if (self.innerHeight)
        {
                x = self.innerWidth;
        }
        else if (document.documentElement && document.documentElement.clientHeight)
        {
                x = document.documentElement.clientWidth;
        }
        else if (document.body)
        {
                x = document.body.clientWidth;
        }
        return x;

}