For fear that downloading the audio and video files behind the website will take up a lot of user traffic, mobile browsers now prohibit audio and video preloading and can only play one sound at a time. When another one is played, the current one will automatically stop and no data will be loaded. Under the user's direct operation, audio and video can be loaded, such as clicking, so the loaded and played code can be placed in the touchstart event (user's direct operation is equivalent to knowing and allowing).