How to find with javascript if element exists in DOM or it's virtual (has been just created by createElement)

Answer 1

Do this:

var elem = document.createElement('div');
elem.setAttribute('id', 'my_new_div');

if (document.getElementById('my_new_div')) { } //element exists in the document.

Answer 2

The safest way is to test directly whether the element is contained in the document:

function isInDocument(el) {
    var html = document.body.parentNode;
    while (el) {
        if (el === html) {
            return true;
        }
        el = el.parentNode;
    }
    return false;
}

var elem = document.createElement('div');
alert(isInDocument(elem));
document.body.appendChild(elem);
alert(isInDocument(elem));

Answer 3

Use compareDocumentPosition to see if the element is contained inside document. PPK has browser compatibility details and John Resig has a version for IE.