on()

on(type, filter, callback): RealtimeChannel

监听频道事件。presence 与 postgres_changes 必须在 subscribe() 之前绑定。

参数

type

"broadcast" | "presence" | "postgres_changes" | "system"

事件类型

filter

object

过滤条件，如 { event } 或 Postgres CDC filter

callback

(payload) => void

事件回调

返回

RealtimeChannel

RealtimeChannel

当前频道，便于链式调用

示例

Broadcast

channel.on("broadcast", { event: "cursor-pos" }, (payload) => {
  console.log(payload.event, payload.payload);
});

Presence

channel
  .on("presence", { event: "sync" }, () => {
    console.log(channel.presenceState());
  })
  .on("presence", { event: "join" }, ({ newPresences }) => {
    console.log(newPresences);
  })
  .on("presence", { event: "leave" }, ({ leftPresences }) => {
    console.log(leftPresences);
  });

Postgres CDC

channel.on(
  "postgres_changes",
  { event: "*", schema: "public", table: "messages" },
  (payload) => {
    console.log(payload.eventType, payload.new, payload.old);
  }
);