Can anybody explain this JS code inside the audio tag?

Question

I'm creating a React app. While looking at this example: https://codepen.io/freeCodeCamp/pen/XpKrrW?editors=0010 I found a peculiar way to manage the audio tag at lines 211 - 213. Can anybody explain to me what the author is doing here?

I looked at the documentation: https://www.w3schools.com/tags/tag_audio.asp but ref isn't even in the default properties.

<audio id="beep" preload="auto" 
    src="<<audio url>>"
    ref={(audio) => { this.audioBeep = audio; }} />

Answer 1

这是一个react属性，请检查此ref函数