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

Question

I\'m trying to get:

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

In my own scripts, I used

Answer 1

differentiate a raw js object from a HTMLElement

function isDOM (x){
     return /HTML/.test( {}.toString.call(x) );
 }

use:

isDOM( {a:1} ) // false
isDOM( document.body ) // true

// OR

Object.defineProperty(Object.prototype, "is",
    {
        value: function (x) {
            return {}.toString.call(this).indexOf(x) >= 0;
        }
    });

use:

o={}; o.is("HTML") // false o=document.body; o.is("HTML") // true

Answer 2

Each DOMElement.constructor returns function HTML...Element() or [Object HTML...Element] so...

function isDOM(getElem){
    if(getElem===null||typeof getElem==="undefined") return false;
    var c = getElem.constructor.toString();
    var html = c.search("HTML")!==-1;
    var element = c.search("Element")!==-1;
    return html&&element;
}

Answer 3

In Firefox, you can use the instanceof Node. That Node is defined in DOM1.

But that is not that easy in IE.

1. "instanceof ActiveXObject" only can tell that it is a native object.
2. "typeof document.body.appendChild=='object'" tell that it may be DOM object, but also can be something else have same function.

You can only ensure it is DOM element by using DOM function and catch if any exception. However, it may have side effect (e.g. change object internal state/performance/memory leak)

Answer 4

var IsPlainObject = function ( obj ) { return obj instanceof Object && ! ( obj instanceof Function || obj.toString( ) !== '[object Object]' || obj.constructor.name !== 'Object' ); },
    IsDOMObject = function ( obj ) { return obj instanceof EventTarget; },
    IsDOMElement = function ( obj ) { return obj instanceof Node; },
    IsListObject = function ( obj ) { return obj instanceof Array || obj instanceof NodeList; },

// In fact I am more likely t use these inline, but sometimes it is good to have these shortcuts for setup code

Answer 5

You could try appending it to a real DOM node...

function isDom(obj)
{
    var elm = document.createElement('div');
    try
    {
        elm.appendChild(obj);
    }
    catch (e)
    {
        return false;
    }

    return true;
}

Answer 6

I suggest a simple way to testing if a variable is an DOM element

function isDomEntity(entity) {
  if(typeof entity  === 'object' && entity.nodeType !== undefined){
     return true;
  }
  else{
     return false;
  }
}

or as HTMLGuy suggested:

const isDomEntity = entity => {
  return typeof entity   === 'object' && entity.nodeType !== undefined
}