如何在React中设置视频端组件的状态？

Question

In my component I have an componentDidUpdate function where I play a video and on that video I set the video.onended event as noted HERE

Currently my code looks like this:

  componentDidUpdate: function() {
    if(this.state.showVideo){
      this.refs.homeVideo.play();
      // Triggering event on video end
      let homeVideo = document.getElementById("homeVideo");
      homeVideo.onended = function(){
        console.log(this.state);
        this.setState({ showVideo: !this.state.showVideo });
      }
    }
  }

My issue right now is that this.state is undefined in the onended function and so is setState, which is preventing me from updating the state of the component in react so that I can close the video player when it ends.

What is the appropriate react way of handling this?

Answer 1

Its because every new function defined its own this value.

You can do something like:

var self = this;
homeVideo.onended = function(){
  console.log(self.state);
  self.setState({ showVideo: !self.state.showVideo });
}

Or better yet, use arrow functions if your using ES6:

homeVideo.onended = () => {
   console.log(this.state);
   this.setState({ showVideo: !this.state.showVideo });
}

Arrow functions lexically binds the this value.

Answer 2

You don't need document.getElementById.

Try to update your code to this:

componentDidUpdate: function() {
    var self = this;
    if(this.state.showVideo){
      let video = this.refs.homeVideo;
      video.play();
      video.onended = function(){
        console.log(self.state);
        self.setState({ showVideo: !self.state.showVideo });
      }
    }
  }

JSfiddle example https://jsfiddle.net/ntfjncuf/