The RTCPeerConnection.ondatachannel property is an event handler which specifies a function which is called when the datachannel event occurs on an RTCPeerConnection. This event, of type RTCDataChannelEvent, is sent when an RTCDataChannel is added to the connection by the remote peer calling createDataChannel(). 
 At the time this event is received, the RTCDataChannel it indicates may not yet actually be open. Be sure to wait for the "open" event to be fired on the new RTCDataChannel before using it. 
RTCPeerConnection.ondatachannel = function;
 Set this property to be a function you provide which receives as input a single parameter: an RTCDataChannelEvent which provides in its channel property the RTCDataChannel which has been created. 
pc.ondatachannel = function(ev) { console.log('Data channel is created!'); ev.channel.onopen = function() { console.log('Data channel is open and ready to be used.'); }; };
| Specification | 
|---|
| WebRTC 1.0: Real-Time Communication Between Browsers (WebRTC 1.0) # dom-rtcpeerconnection-ondatachannel  | 
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | |
ondatachannel | 
25  | 
79  | 
22  | 
No  | 
15  | 
11  | 
≤37  | 
25  | 
44  | 
14  | 
11  | 
1.5  | 
datachannel event and its type, RTCDataChannelEvent.RTCPeerConnection.createDataChannel()
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    https://developer.mozilla.org/en-US/docs/Web/API/RTCPeerConnection/ondatachannel