自定义CSS无法覆盖Bootstrap CSS的技术问询

要实现.navbar-nav容器内<a>标签hover时显示红色，且无需使用!important，只需提升自定义CSS选择器的权重即可。

原因分析 #

Bootstrap中控制导航链接hover样式的选择器是.nav-link.link-light:hover，其CSS权重为30（两个类选择器+一个伪类选择器）。你原有的选择器.navbar-nav a:hover权重仅为21（一个类选择器+一个元素选择器+一个伪类选择器），权重不足导致无法覆盖Bootstrap的默认样式。

修改后的核心CSS代码 #

将原有hover样式代码替换为：

.navbar-nav .nav-link:hover {
  color: red;
}

该选择器权重为30（两个类选择器+一个伪类选择器），与Bootstrap的目标选择器权重持平，且由于自定义CSS在Bootstrap之后加载，会优先生效。

完整修改后的CSS片段 #

/* http://meyerweb.com/eric/tools/css/reset/ 
   v2.0 | 20110126
   License: none (public domain)
*/

html,
body,
div,
span,
applet,
object,
iframe,
h1,
h2,
h3,
h4,
h5,
h6,
p,
blockquote,
pre,
a,
abbr,
acronym,
address,
big,
cite,
code,
del,
dfn,
em,
img,
ins,
kbd,
q,
s,
samp,
small,
strike,
strong,
sub,
sup,
tt,
var,
b,
u,
i,
center,
dl,
dt,
dd,
ol,
ul,
li,
fieldset,
form,
label,
legend,
table,
caption,
tbody,
tfoot,
thead,
tr,
th,
td,
article,
aside,
canvas,
details,
embed,
figure,
figcaption,
footer,
header,
hgroup,
menu,
nav,
output,
ruby,
section,
summary,
time,
mark,
audio,
video {
  margin: 0;
  padding: 0;
  border: 0;
  font-size: 100%;
  font: inherit;
  vertical-align: baseline;
}

/* HTML5 display-role reset for older browsers */
article,
aside,
details,
figcaption,
figure,
footer,
header,
hgroup,
menu,
nav,
section {
  display: block;
}

body {
  line-height: 1;
}

ol,
ul {
  list-style: none;
}

blockquote,
q {
  quotes: none;
}

blockquote:before,
blockquote:after,
q:before,
q:after {
  content: '';
  content: none;
}

table {
  border-collapse: collapse;
  border-spacing: 0;
}

html {
  box-sizing: border-box;
  font-family: sans-serif;
  line-height: 1.15;
}

body {
  background-color: #F4D9D5;
}

.navbar-brand,
.navbar-nav {
  font-size: 1.5rem;
  font-weight: 100;
}

.navbar-nav .nav-link:hover {
  color: red;
}

内容的提问来源于stack exchange，提问作者Pradyut Vatsa