JavaScript Snippet - WordPress Window-Messaging Semi-Safe Example

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/**
 * WordPress inline HTML embed
 *
 * @since 4.4.0
 *
 * This file cannot have ampersands in it. This is to ensure
 * it can be embedded in older versions of WordPress.
 * See https://core.trac.wordpress.org/changeset/35708.
 */
(function ( window, document ) {
'use strict';

var supportedBrowser = false,
loaded = false;

if ( document.querySelector ) {
if ( window.addEventListener ) {
supportedBrowser = true;
}
}

window.wp = window.wp || {};

if ( !! window.wp.receiveEmbedMessage ) {
return;
}

window.wp.receiveEmbedMessage = function( e ) {
var data = e.data;
if ( ! ( data.secret || data.message || data.value ) ) {
return;
}

if ( /[^a-zA-Z0-9]/.test( data.secret ) ) {
return;
}

var iframes = document.querySelectorAll( 'iframe[data-secret="' + data.secret + '"]' ),
blockquotes = document.querySelectorAll( 'blockquote[data-secret="' + data.secret + '"]' ),
i, source, height, sourceURL, targetURL;

for ( i = 0; i < blockquotes.length; i++ ) {
blockquotes[ i ].style.display = 'none';
}

for ( i = 0; i < iframes.length; i++ ) {
source = iframes[ i ];

if ( e.source !== source.contentWindow ) {
continue;
}

source.removeAttribute( 'style' );

/* Resize the iframe on request. */
if ( 'height' === data.message ) {
height = parseInt( data.value, 10 );
if ( height > 1000 ) {
height = 1000;
} else if ( ~~height < 200 ) {
height = 200;
}

source.height = height;
}

/* Link to a specific URL on request. */
if ( 'link' === data.message ) {
sourceURL = document.createElement( 'a' );
targetURL = document.createElement( 'a' );

sourceURL.href = source.getAttribute( 'src' );
targetURL.href = data.value;

/* Only continue if link hostname matches iframe's hostname. */
if ( targetURL.host === sourceURL.host ) {
if ( document.activeElement === source ) {
window.top.location.href = data.value;
}
}
}
}
};

function onLoad() {
if ( loaded ) {
return;
}

loaded = true;

var isIE10 = -1 !== navigator.appVersion.indexOf( 'MSIE 10' ),
isIE11 = !!navigator.userAgent.match( /Trident.*rv:11\\./ ),
iframes = document.querySelectorAll( 'iframe.wp-embedded-content' ),
iframeClone, i, source, secret;

for ( i = 0; i < iframes.length; i++ ) {
source = iframes[ i ];

if ( source.getAttribute( 'data-secret' ) ) {
continue;
}

/* Add secret to iframe */
secret = Math.random().toString( 36 ).substr( 2, 10 );
source.src += '#?secret=' + secret;
source.setAttribute( 'data-secret', secret );

/* Remove security attribute from iframes in IE10 and IE11. */
if ( ( isIE10 || isIE11 ) ) {
iframeClone = source.cloneNode( true );
iframeClone.removeAttribute( 'security' );
source.parentNode.replaceChild( iframeClone, source );
}
}
}

if ( supportedBrowser ) {
window.addEventListener( 'message', window.wp.receiveEmbedMessage, false );
document.addEventListener( 'DOMContentLoaded', onLoad, false );
window.addEventListener( 'load', onLoad, false );
}
})( window, document );