如何在类中设置动态高度：在使用jquery之前？(how to set dynamic height in class:before using jquery?)

 如何设置屏幕高度到我的班级：之前？ 我厌倦了使用jquery这样做。 这是我的代码： 
 
var login_height = $(window).height();     
$(".login_left_box:before").css('border-bottom-width' , login_height+"px");
 
 在这里我设置动态border-bottom-width： 1024px在这个类中（设置1024px动态）所以我怎么能？ 
 
.login_left_box:before {
    content: "";
    width: 0px;
    height: 0px;
    border-bottom: 750px solid #fff;
    border-left: 100px solid transparent;
    position: absolute;
    right: 0;
    top: 0px;
    background-image: url(../images/common/bg.png);
    background-repeat: no-repeat;
    background-size: cover;
    border-bottom-width: 1024px;
}

how to set screen height to my class :before ? i tired to do this using jquery. here is my code:
 
var login_height = $(window).height();     
$(".login_left_box:before").css('border-bottom-width' , login_height+"px");
 
and here i set dynamic border-bottom-width: 1024px in this class(set 1024px dynamic) so how can i ?
 
.login_left_box:before {
    content: "";
    width: 0px;
    height: 0px;
    border-bottom: 750px solid #fff;
    border-left: 100px solid transparent;
    position: absolute;
    right: 0;
    top: 0px;
    background-image: url(../images/common/bg.png);
    background-repeat: no-repeat;
    background-size: cover;
    border-bottom-width: 1024px;
}

原文：https://stackoverflow.com/questions/43062717