my.offCompassChange

Page({
  onLoad() {
    my.onCompassChange(this.handleCompass);
  },

  handleCompass(res) {
    console.log('Heading:', res.direction);
  },

  onUnload() {
    my.offCompassChange(this.handleCompass);
  }
});

// Remove all compass listeners
my.offCompassChange();

Page({
  data: {
    compassActive: false
  },

  toggleCompass() {
    if (this.data.compassActive) {
      my.offCompassChange(this.updateHeading);
      this.setData({ compassActive: false });
    } else {
      my.startCompass();
      my.onCompassChange(this.updateHeading);
      this.setData({ compassActive: true });
    }
  },

  updateHeading(res) {
    this.setData({ heading: res.direction });
  }
});