Native Js realizes elements fading/appearing (the principle is to modify the css transparency of elements)_javascript skills

I often see gradient displays of images on web pages, so I decided to write one myself.
The principle is very simple: modify the CSS transparency of the element.
Online preview: http://jsfiddle.net/dtdxrk/BHUp9/embedded/result/

Copy code Code As follows:

fade in
fade in