问题
I want to be able to control iframe based YouTube players. This players will be already in the HTML, but I want to control them via the JavaScript API.
I've been reading the documentation for the iframe API which explain how to add a new video to the page with the API, and then control it with the YouTube player functions:
var player;
function onYouTubePlayerAPIReady() {
player = new YT.Player('container', {
height: '390',
width: '640',
videoId: 'u1zgFlCw8Aw',
events: {
'onReady': onPlayerReady,
'onStateChange': onPlayerStateChange
}
});
}
That code creates a new player object and assigns it to 'player', then inserts it inside the #container div. Then I can operate on 'player' and call playVideo(), pauseVideo(), etc. on it.
But I want to be able to operate on iframe players which are already on the page.
I could do this very easily with the old embed method, with something like:
player = getElementById('whateverID');
player.playVideo();
But this doesn't work with the new iframes. How can I assign a iframe object already on the page and then use the API functions on it?
回答1:
Fiddle Links: Source code - Preview - Small version
Update: This small function will only execute code in a single direction. If you want full support (eg event listeners / getters), have a look at Listening for Youtube Event in jQuery
As a result of a deep code analysis, I've created a function: function callPlayer requests a function call on any framed YouTube video. See the YouTube Api reference to get a full list of possible function calls. Read the comments at the source code for an explanation.
On 17 may 2012, the code size was doubled in order to take care of the player's ready state. If you need a compact function which does not deal with the player's ready state, see http://jsfiddle.net/8R5y6/.
/**
* @author Rob W <gwnRob@gmail.com>
* @website https://stackoverflow.com/a/7513356/938089
* @version 20190409
* @description Executes function on a framed YouTube video (see website link)
* For a full list of possible functions, see:
* https://developers.google.com/youtube/js_api_reference
* @param String frame_id The id of (the div containing) the frame
* @param String func Desired function to call, eg. "playVideo"
* (Function) Function to call when the player is ready.
* @param Array args (optional) List of arguments to pass to function func*/
function callPlayer(frame_id, func, args) {
if (window.jQuery && frame_id instanceof jQuery) frame_id = frame_id.get(0).id;
var iframe = document.getElementById(frame_id);
if (iframe && iframe.tagName.toUpperCase() != 'IFRAME') {
iframe = iframe.getElementsByTagName('iframe')[0];
}
// When the player is not ready yet, add the event to a queue
// Each frame_id is associated with an own queue.
// Each queue has three possible states:
// undefined = uninitialised / array = queue / .ready=true = ready
if (!callPlayer.queue) callPlayer.queue = {};
var queue = callPlayer.queue[frame_id],
domReady = document.readyState == 'complete';
if (domReady && !iframe) {
// DOM is ready and iframe does not exist. Log a message
window.console && console.log('callPlayer: Frame not found; id=' + frame_id);
if (queue) clearInterval(queue.poller);
} else if (func === 'listening') {
// Sending the "listener" message to the frame, to request status updates
if (iframe && iframe.contentWindow) {
func = '{"event":"listening","id":' + JSON.stringify(''+frame_id) + '}';
iframe.contentWindow.postMessage(func, '*');
}
} else if ((!queue || !queue.ready) && (
!domReady ||
iframe && !iframe.contentWindow ||
typeof func === 'function')) {
if (!queue) queue = callPlayer.queue[frame_id] = [];
queue.push([func, args]);
if (!('poller' in queue)) {
// keep polling until the document and frame is ready
queue.poller = setInterval(function() {
callPlayer(frame_id, 'listening');
}, 250);
// Add a global "message" event listener, to catch status updates:
messageEvent(1, function runOnceReady(e) {
if (!iframe) {
iframe = document.getElementById(frame_id);
if (!iframe) return;
if (iframe.tagName.toUpperCase() != 'IFRAME') {
iframe = iframe.getElementsByTagName('iframe')[0];
if (!iframe) return;
}
}
if (e.source === iframe.contentWindow) {
// Assume that the player is ready if we receive a
// message from the iframe
clearInterval(queue.poller);
queue.ready = true;
messageEvent(0, runOnceReady);
// .. and release the queue:
while (tmp = queue.shift()) {
callPlayer(frame_id, tmp[0], tmp[1]);
}
}
}, false);
}
} else if (iframe && iframe.contentWindow) {
// When a function is supplied, just call it (like "onYouTubePlayerReady")
if (func.call) return func();
// Frame exists, send message
iframe.contentWindow.postMessage(JSON.stringify({
"event": "command",
"func": func,
"args": args || [],
"id": frame_id
}), "*");
}
/* IE8 does not support addEventListener... */
function messageEvent(add, listener) {
var w3 = add ? window.addEventListener : window.removeEventListener;
w3 ?
w3('message', listener, !1)
:
(add ? window.attachEvent : window.detachEvent)('onmessage', listener);
}
}
Usage:
callPlayer("whateverID", function() {
// This function runs once the player is ready ("onYouTubePlayerReady")
callPlayer("whateverID", "playVideo");
});
// When the player is not ready yet, the function will be queued.
// When the iframe cannot be found, a message is logged in the console.
callPlayer("whateverID", "playVideo");
Possible questions (& answers):
Q: It doesn't work!
A: "Doesn't work" is not a clear description. Do you get any error messages? Please show the relevant code.
Q: playVideo does not play the video.
A: Playback requires user interaction, and the presence of allow="autoplay" on the iframe. See https://developers.google.com/web/updates/2017/09/autoplay-policy-changes and https://developer.mozilla.org/en-US/docs/Web/Media/Autoplay_guide
Q: I have embedded a YouTube video using <iframe src="http://www.youtube.com/embed/As2rZGPGKDY" />but the function doesn't execute any function!
A: You have to add ?enablejsapi=1 at the end of your URL: /embed/vid_id?enablejsapi=1.
Q: I get error message "An invalid or illegal string was specified". Why?
A: The API doesn't function properly at a local host (file://). Host your (test) page online, or use JSFiddle. Examples: See the links at the top of this answer.
Q: How did you know this?
A: I have spent some time to manually interpret the API's source. I concluded that I had to use the postMessage method. To know which arguments to pass, I created a Chrome extension which intercepts messages. The source code for the extension can be downloaded here.
Q: What browsers are supported?
A: Every browser which supports JSON and postMessage.
- IE 8+
- Firefox 3.6+ (actually 3.5, but
document.readyStatewas implemented in 3.6) - Opera 10.50+
- Safari 4+
- Chrome 3+
Related answer / implementation: Fade-in a framed video using jQuery
Full API support: Listening for Youtube Event in jQuery
Official API: https://developers.google.com/youtube/iframe_api_reference
Revision history
- 17 may 2012
ImplementedonYouTubePlayerReady:callPlayer('frame_id', function() { ... }).
Functions are automatically queued when the player is not ready yet. - 24 july 2012
Updated and successully tested in the supported browsers (look ahead). - 10 october 2013
When a function is passed as an argument,
callPlayerforces a check of readiness. This is needed, because whencallPlayeris called right after the insertion of the iframe while the document is ready, it can't know for sure that the iframe is fully ready. In Internet Explorer and Firefox, this scenario resulted in a too early invocation ofpostMessage, which was ignored. - 12 Dec 2013, recommended to add
&origin=*in the URL. - 2 Mar 2014, retracted recommendation to remove
&origin=*to the URL. - 9 april 2019, fix bug that resulted in infinite recursion when YouTube loads before the page was ready. Add note about autoplay.
回答2:
Looks like YouTube has updated their JS API so this is available by default! You can use an existing YouTube iframe's ID...
<iframe id="player" src="http://www.youtube.com/embed/M7lc1UVf-VE?enablejsapi=1&origin=http://example.com" frameborder="0"></iframe>
...in your JS...
var player;
function onYouTubeIframeAPIReady() {
player = new YT.Player('player', {
events: {
'onStateChange': onPlayerStateChange
}
});
}
function onPlayerStateChange() {
//...
}
...and the constructor will use your existing iframe instead of replacing it with a new one. This also means you don't have to specify the videoId to the constructor.
See Loading a video player
回答3:
You can do this with far less code:
function callPlayer(func, args) {
var i = 0,
iframes = document.getElementsByTagName('iframe'),
src = '';
for (i = 0; i < iframes.length; i += 1) {
src = iframes[i].getAttribute('src');
if (src && src.indexOf('youtube.com/embed') !== -1) {
iframes[i].contentWindow.postMessage(JSON.stringify({
'event': 'command',
'func': func,
'args': args || []
}), '*');
}
}
}
Working example: http://jsfiddle.net/kmturley/g6P5H/296/
回答4:
My own version of Kim T's code above which combines with some jQuery and allows for targeting of specific iframes.
$(function() {
callPlayer($('#iframe')[0], 'unMute');
});
function callPlayer(iframe, func, args) {
if ( iframe.src.indexOf('youtube.com/embed') !== -1) {
iframe.contentWindow.postMessage( JSON.stringify({
'event': 'command',
'func': func,
'args': args || []
} ), '*');
}
}
来源：https://stackoverflow.com/questions/7443578/youtube-iframe-api-how-do-i-control-a-iframe-player-thats-already-in-the-html