get audio duration in wechat MINA app

get_duration_mina.js

getDuration: function(audio, id) {
    const {
      durations = {},
        retry = {}
    } = this.data;
    let {
      duration
    } = audio;
    console.info('audio.duration', audio.duration);
    if (duration == 0) {
      retry[id] = retry[id] || 0;
      return setTimeout(() => {
        if (retry[id] > 10) { // retry at most 9 times
          return
        }
        retry[id] += 1;
        this.setData({
          retry
        });
        this.getDuration(audio, id)
      }, 300);
    }
    retry[id] = 0;
    durations[id] = this.timeFormat(duration);
    this.setData({
      durations,
      retry
    });
  }

@params id, the unique id of audio stored in DB