Check if Dom Element is Native / no Custom Element

Question

Is there a way to check whether a Dom Element is a Native Element or a (not resolved) Custom Element without checking all Native tagNames in Javascript?

I Already thought of checking on element.constructor === HTMLElement but the <main> (documentation) tag has that as it's top level class.

Basically I need a faster and less maintenance intensive way of checking for a native element.

Answer 1

So after the comment of Supersharp I found out that all custom elements tagName or the is attribute must contain a hyphen and native elements never do, so the best way to figure that out is to use this function:

function isCustomElement(element){
    if(element.tagName.indexOf("-") !== -1) {
        return true;
    }
    let isAttribute = element.getAttribute("is");
    if(isAttribute === null) {
        return false;
    }
    return isAttribute.indexOf("-") !== -1;
}

Simple as that.

The W3C Standard documentation:

They contain a hyphen, used for namespacing and to ensure forward compatibility (since no elements will be added to HTML, SVG, or MathML with hyphen-containing local names in the future).