微信小程序websocket通信的前端DEMO，已测可以！

app.js

在app.js下添加三个函数openSocket()， closeSocket()，sendMessage()，在app初始化的onLunch函数里面调用openSocket()，这样子用户一进入小程序就会自动连接websocket

App({
      globalData: {
        socketStatus: 'closed',
      },
    onLaunch: function() {   
        var that = this;
        if (that.globalData.socketStatus === 'closed') {
              that.openSocket();
        }
    }
    openSocket() {
       //打开时的动作
        wx.onSocketOpen(() => {
          console.log('WebSocket 已连接')
          this.globalData.socketStatus = 'connected';
          this.sendMessage();
        })
        //断开时的动作
        wx.onSocketClose(() => {
          console.log('WebSocket 已断开')
          this.globalData.socketStatus = 'closed'
        })
        //报错时的动作
        wx.onSocketError(error => {
          console.error('socket error:', error)
        })
        // 监听服务器推送的消息
        wx.onSocketMessage(message => {
          //把JSONStr转为JSON
          message = message.data.replace(" ", "");
          if (typeof message != 'object') {
            message = message.replace(/\ufeff/g, ""); //重点
            var jj = JSON.parse(message);
            message = jj;
          }
          console.log("【websocket监听到消息】内容如下：");
          console.log(message);
        })
        // 打开信道
        wx.connectSocket({
          url: "ws://" + "localhost" + ":8888",
        })
      },
        
    //关闭信道
      closeSocket() {
        if (this.globalData.socketStatus === 'connected') {
          wx.closeSocket({
            success: () => {
              this.globalData.socketStatus = 'closed'
            }
          })
        }
      },
        
     //发送消息函数
      sendMessage() {
        if (this.globalData.socketStatus === 'connected') {
        //自定义的发给后台识别的参数 ，我这里发送的是name
          wx.sendSocketMessage({
            data: "{\"name\":\"" + wx.getStorageSync('openid') + "\"}"  
          })
        }
      },
})