Pseudo element Clear float? Do you understand this?

With the development of the front-end, the face of floating this problem we generally like to use pseudo-elements to clear the float, the following style is known as universal clear floating

. clearfix:after {content: "."; Display: block; height:0; clear:both;}

. clearfix {zoom:1;}

It looks like there's nothing wrong with it, but recently my little brother has a problem (360 speed browser):

A pseudo-element is a block-level element that clears the float after the clearfix element and fills it with content, but some browsers produce this for example "." The problem of placeholder (in the actual production environment),

The younger brother examines the half-day only to discover is this question, therefore the content contents carries on the emptying, the result solves the problem!

Which great God has a deeper understanding? Please advise!

Pseudo element Clear float? Do you understand this?