How do you check if a JavaScript Object is a DOM Object?

I'm trying to get:

document.createElement('div')  //=> true
{tagName: 'foobar something'}  //=> false

In my own scripts, I used to just use this since I never needed tagName as a property:

if (!object.tagName) throw ...;

So for the second object, I came up with the following as a quick solution -- which mostly works. ;)

The problem is, it depends on browsers enforcing read-only properties, which not all do.

function isDOM(obj) {
  var tag = obj.tagName;
  try {
    obj.tagName = '';  // Read-only for DOM, should throw exception
    obj.tagName = tag; // Restore for normal objects
    return false;
  } catch (e) {
    return true;
  }
}

Is there a good substitute?

Solution 1:

This might be of interest:

function isElement(obj) {
  try {
    //Using W3 DOM2 (works for FF, Opera and Chrome)
    return obj instanceof HTMLElement;
  }
  catch(e){
    //Browsers not supporting W3 DOM2 don't have HTMLElement and
    //an exception is thrown and we end up here. Testing some
    //properties that all elements have (works on IE7)
    return (typeof obj==="object") &&
      (obj.nodeType===1) && (typeof obj.style === "object") &&
      (typeof obj.ownerDocument ==="object");
  }
}

It's part of the DOM, Level2.

Update 2: This is how I implemented it in my own library: (the previous code didn't work in Chrome, because Node and HTMLElement are functions instead of the expected object. This code is tested in FF3, IE7, Chrome 1 and Opera 9).

//Returns true if it is a DOM node
function isNode(o){
  return (
    typeof Node === "object" ? o instanceof Node : 
    o && typeof o === "object" && typeof o.nodeType === "number" && typeof o.nodeName==="string"
  );
}

//Returns true if it is a DOM element    
function isElement(o){
  return (
    typeof HTMLElement === "object" ? o instanceof HTMLElement : //DOM2
    o && typeof o === "object" && o !== null && o.nodeType === 1 && typeof o.nodeName==="string"
);
}

Solution 2:

The following IE8 compatible, super-simple code works perfectly.

The accepted answer does not detect all types of HTML elements. For example, SVG elements are not supported. In contrast, this answer works for HTML well as SVG.

See it in action here: https://jsfiddle.net/eLuhbu6r/

function isElement(element) {
    return element instanceof Element || element instanceof HTMLDocument;  
}

Solution 3:

No need for hacks, you can just ask if an element is an instance of the DOM Element:

const isDOM = el => el instanceof Element