HTMLIFrameElement.contentWindow

The contentWindow property returns the Window object of an <iframe> element. You can use this Window object to access the iframe's document and its internal DOM. This attribute is read-only, but its properties can be manipulated like the global Window object.

Example of contentWindow

var x = document.getElementsByTagName("iframe")[0].contentWindow;
//x = window.frames[0];

x.document.getElementsByTagName("body")[0].style.backgroundColor = "blue";
// this would turn the 1st iframe in document blue.

Browser compatibility