How to check if a DOM node is the `html` node

Question

EDIT: This is the dumbest question I've asked on SO. I'll keep it, to remind myself not to ask questions too quickly.

How can I check if the DOM node I have selected is the html node? I have noticed that it does not have the usual properties. For example:

var div = document.getElementsByTagName('div')[0];
var html = document.getElementsByTagName('html');

div instanceof HTMLElement; // true
html instanceof HTMLElement; // false

div.tagName; // "DIV"
html.tagName; // undefined

In particular, I would like a check that works for all DOM nodes (div, span, etc.). The issue is that my code crawls up the DOM and checks for a certain property; if the code does not find the property, it reaches the html node and throws an error because of this line:

if (node.tagName.toUpperCase() !== 'OBJECT') { }

This throws a TypeError when node is the html node, because node.TagName is undefined.

Thanks in advance.

p.s.w.g · Accepted Answer · 2013-10-22 20:53:40Z

2

The problem is that you are looking at the array returned by getElementsByTagName instead of the first element returned. Try this:

var div = document.getElementsByTagName('div')[0];
var html = document.getElementsByTagName('html')[0]; // notice [0]

div instanceof HTMLElement; // true
html instanceof HTMLElement; // true

div.tagName; // "DIV"
html.tagName; // "HTML"

^{Note: tested in in Chrome Developer Tools Version 30.0.1599.101 m}

answered Oct 22, 2013 at 20:53

p.s.w.g

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epascarello · Accepted Answer · 2013-10-22 20:52:38Z

1

Your variable html is not a single node, hence why it is different than div. Add the missing [0] like you do for your div reference!

answered Oct 22, 2013 at 20:52

epascarello

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1 Comment

EmmyS Over a year ago

Yeah, in the console you will get an undefined, because you're setting a var but not doing anything with it. Try var html = document.getElementsByTagName('html')[0]; console.log(html); This will produce an expandable tree of the html node.

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