how to change element inside of an iframe with javascript code example

Example 1: iframe getelementbyid

document.getElementById('myframe1').contentWindow.document.getElementById('x')

Example 2: change element in iframe

// so you got an iframe (id="myiframe"). In that page you have an element id="theprice" and you want to change its value
// from the parent page do this in your javascript:
var iframevar = document.getElementById('myiframe');
var elmnt = iframevar.contentWindow.document.getElementById("theprice");
elmnt.innerHTML = theNewPrice;