AddToDOM = function (element, parent)
{
    var target;

    if (parent)
    {
        if (typeof parent === 'string')
        {
            //  Hopefully an element ID
            target = document.getElementById(parent);
        }
        else if (typeof parent === 'object' && parent.nodeType === 1)
        {
            //  Quick test for a HTMLElement
            target = parent;
        }
    }
    else if (element.parentElement || parent === null)
    {
        return element;
    }

    //  Fallback, covers an invalid ID and a non HTMLElement object
    if (!target)
    {
        target = document.body;
    }

    target.appendChild(element);

    return element;
}
Adds the given element to the DOM. If a parent is provided the element is added as a child of the parent, providing it was able to access it.
If no parent was given it falls back to using `document.body`.

@function Phaser.DOM.AddToDOM
@since 3.0.0

@param {HTMLElement} element - The element to be added to the DOM. Usually a Canvas object.
@param {(string|HTMLElement)} [parent] - The parent in which to add the element. Can be a string which is passed to `getElementById` or an actual DOM object.

@return {HTMLElement} The element that was added to the DOM.