postMessage - To: Information and samples for HTML5 and related APIs

Code used in this page

					window.onload = function () {
						var iframeWin = document.getElementById("da-iframe").contentWindow,
							form = document.getElementById("the-form"),
							myMessage = document.getElementById("my-message");

						myMessage.select();

						form.onsubmit = function () {
							iframeWin.postMessage(myMessage.value, "https://robertnyman.com");
							return false;
						};
					};
				

Code used in the iframe

					function displayMessage (evt) {
						var message;
						if (evt.origin !== "https://robertnyman.com") {
							message = "You are not worthy";
						}
						else {
							message = "I got " + evt.data + " from " + evt.origin;
						}
						document.getElementById("received-message").innerHTML = message;
					}

					if (window.addEventListener) {
						// For standards-compliant web browsers
						window.addEventListener("message", displayMessage, false);
					}
					else {
						window.attachEvent("onmessage", displayMessage);
					}