The applet listens for the target node to appear on the screen

The applet makes a card in the list and appears on the phone screen , Show read status practice ：

 onReady() {
    this.changeSign()
    this.param = JSON.parse(JSON.stringify(this.itemData))
    uni.createIntersectionObserver(this).relativeToViewport({ bottom: -160 }).observe('.content', (res) => {
      if (this.itemData.readingState === 0) {
        this.clearRed()
      }
    })
  },

Applet list each card is encapsulated with components , stay onReady Call in , Judge to call the read interface in the unread state