从浏览器发送websocket ping / pong框架

I keep reading about ping/pong messages in websockets to keep the connection alive, but I'm not sure what they are. Is it a distinct frame type? (I don't see any methods on a javascript WebSocket object in chrome related to ping-pong). Or is it just a design pattern (e.g. I literally send "ping" or any other string to the server and have it respond). Is ping-pong at all related to continuation frames?I keep reading about ping/pong messages in webs