how does the dom know which html document you're on code example
Example 1: what is document object
document.anchors Returns all <a> elements that have a name attribute 1
document.applets Returns all <applet> elements (Deprecated in HTML5) 1
document.baseURI Returns the absolute base URI of the document 3
document.body Returns the <body> element 1
document.cookie Returns the document's cookie 1
document.doctype Returns the document's doctype 3
document.documentElement Returns the <html> element 3
document.documentMode Returns the mode used by the browser 3
document.documentURI Returns the URI of the document 3
document.domain Returns the domain name of the document server 1
document.embeds Returns all <embed> elements 3
document.forms Returns all <form> elements 1
document.head Returns the <head> element 3
document.images Returns all <img> elements 1
document.implementation Returns the DOM implementation 3
document.inputEncoding Returns the document's encoding (character set) 3
document.lastModified Returns the date and time the document was updated 3
document.links Returns all <area> and <a> elements that have a href attribute 1
document.readyState Returns the (loading) status of the document 3
document.referrer Returns the URI of the referrer (the linking document) 1
document.scripts Returns all <script> elements 3
document.strictErrorChecking Returns if error checking is enforced 3
document.title Returns the <title> element 1
document.URL Returns the complete URL of the document 1
Example 2: DOM
<body onload="window.alert('Welcome to my home page!');">