Only one

by Joshua Koudys

HTML

<iframe class="youtube" width="560" height="315" src="https://www.youtube.com/embed/MepXBJjsNxs" frameborder="0" allowfullscreen></iframe>
<iframe class="youtube" width="560" height="315" src="https://www.youtube.com/embed/O0RU_Nyr4l4" frameborder="0" allowfullscreen></iframe>

JavaScript

document.addEventListener('DOMContentLoaded', function () {
    // Needed for keycodes - thanks http://stackoverflow.com/questions/596481/simulate-javascript-key-events
    var keyboardEvent = document.createEvent("KeyboardEvent");
    var initMethod = typeof keyboardEvent.initKeyboardEvent !== 'undefined' ? "initKeyboardEvent" : "initKeyEvent";
    keyboardEvent[initMethod](
        "keydown", // event type : keydown, keyup, keypress
    true, // bubbles
    true, // cancelable
    window, // viewArg: should be window
    false, // ctrlKeyArg
    false, // altKeyArg
    false, // shiftKeyArg
    false, // metaKeyArg
    32, // keyCodeArg : unsigned long the virtual key code, else 0
    0 // charCodeArgs : unsigned long the Unicode character associated with the depressed key, else 0
    );

    var vids = document.querySelectorAll('.youtube');
    var windows = [];
    [].forEach.call(vids, function (video) {
        // Build window list of iframes
        video.addEventListener('mouseenter', function (ev) {
            [].forEach.call(vids, function (othervid) {
                if (othervid !== video) {
                    debugger;
                    video.contentWindow.document.dispatchEvent(keyboardEvent);
                }
            });
        });
    });
});