Should i use innerhtml or textcontent for the header?

Value

A string containing the HTML serialization of the element's descendants. Setting the value of innerHTML removes all of the element's descendants and replaces them with nodes constructed by parsing the HTML given in the string htmlString.

Exceptions

SyntaxError DOMException

Thrown if an attempt was made to set the value of innerHTML using a string which is not properly-formed HTML.

Thrown if an attempt was made to insert the HTML into a node whose parent is a Document.

Usage notes

The innerHTML property can be used to examine the current HTML source of the page, including any changes that have been made since the page was initially loaded.

Reading the HTML contents of an element

Reading innerHTML causes the user agent to serialize the HTML or XML fragment comprised of the element's descendants. The resulting string is returned.

let contents = myElement.innerHTML;

This lets you look at the HTML markup of the element's content nodes.

Note: The returned HTML or XML fragment is generated based on the current contents of the element, so the markup and formatting of the returned fragment is likely not to match the original page markup.

Replacing the contents of an element

Setting the value of innerHTML lets you easily replace the existing contents of an element with new content.

Note: This is a security risk if the string to be inserted might contain potentially malicious content. When inserting user-supplied data you should always consider using Element.SetHTML[] instead, in order to sanitize the content before it is inserted.

For example, you can erase the entire contents of a document by clearing the contents of the document's body attribute:

document.body.innerHTML = "";

This example fetches the document's current HTML markup and replaces the "