<div class="navbar navbar-fixed-bottom"></div>

这是来自github项目的CSS(bootstrap sass)

// Fix the top/bottom navbars when screen real estate supports it
.navbar-fixed-top,.navbar-fixed-bottom {
  position: fixed;
  right: 0;
  left: 0;
  border-width: 0 0 1px;

  // Undo the rounded corners
  @media (min-width: $grid-float-breakpoint) {
    border-radius: 0;
  }
}
.navbar-fixed-top {
  z-index: $zindex-navbar-fixed;
  top: 0;
}
.navbar-fixed-bottom {
  bottom: 0;
  margin-bottom: 0; // override .navbar defaults
}

我相信这是由于在加载页面后JS呈现内容呈现而发生的.

有没有办法解决这个问题,而不知道JS内容的垂直高度提前？

编辑

这是导航栏上方的容器DIV的CSS：

-webkit-animation-delay: 0s;
-webkit-animation-direction: normal;
-webkit-animation-duration: 0s;
-webkit-animation-fill-mode: none;
-webkit-animation-iteration-count: 1;
-webkit-animation-name: none;
-webkit-animation-play-state: running;
-webkit-animation-timing-function: ease;
-webkit-app-region: no-drag;
-webkit-appearance: none;
-webkit-backface-visibility: visible;
-webkit-background-clip: border-Box;
-webkit-background-composite: source-over;
-webkit-background-origin: padding-Box;
-webkit-background-size: auto;
-webkit-border-fit: border;
-webkit-border-horizontal-spacing: 0px;
-webkit-border-image: none;
-webkit-border-vertical-spacing: 0px;
-webkit-Box-align: stretch;
-webkit-Box-decoration-break: slice;
-webkit-Box-direction: normal;
-webkit-Box-flex: 0;
-webkit-Box-flex-group: 1;
-webkit-Box-lines: single;
-webkit-Box-ordinal-group: 1;
-webkit-Box-orient: horizontal;
-webkit-Box-pack: start;
-webkit-Box-reflect: none;
-webkit-Box-shadow: none;
-webkit-clip-path: none;
-webkit-column-axis: auto;
-webkit-column-break-after: auto;
-webkit-column-break-before: auto;
-webkit-column-break-inside: auto;
-webkit-column-count: auto;
-webkit-column-gap: normal;
-webkit-column-progression: normal;
-webkit-column-rule-color: rgb(51,51,51);
-webkit-column-rule-style: none;
-webkit-column-rule-width: 0px;
-webkit-column-span: none;
-webkit-column-width: auto;
-webkit-filter: none;
-webkit-font-kerning: auto;
-webkit-font-smoothing: auto;
-webkit-font-variant-ligatures: normal;
-webkit-highlight: none;
-webkit-hyphenate-character: auto;
-webkit-hyphenate-limit-after: auto;
-webkit-hyphenate-limit-before: auto;
-webkit-hyphenate-limit-lines: no-limit;
-webkit-hyphens: manual;
-webkit-line-align: none;
-webkit-line-Box-contain: block inline replaced;
-webkit-line-break: auto;
-webkit-line-clamp: none;
-webkit-line-grid: none;
-webkit-line-snap: none;
-webkit-locale: auto;
-webkit-margin-after-collapse: collapse;
-webkit-margin-before-collapse: collapse;
-webkit-marquee-direction: auto;
-webkit-marquee-increment: 6px;
-webkit-marquee-repetition: infinite;
-webkit-marquee-style: scroll;
-webkit-mask-Box-image: none;
-webkit-mask-Box-image-outset: 0px;
-webkit-mask-Box-image-repeat: stretch;
-webkit-mask-Box-image-slice: 0 fill;
-webkit-mask-Box-image-source: none;
-webkit-mask-Box-image-width: auto;
-webkit-mask-clip: border-Box;
-webkit-mask-composite: source-over;
-webkit-mask-image: none;
-webkit-mask-origin: border-Box;
-webkit-mask-position: 0% 0%;
-webkit-mask-repeat: repeat;
-webkit-mask-size: auto;
-webkit-perspective: none;
-webkit-perspective-origin: 585px 196px;
-webkit-print-color-adjust: economy;
-webkit-rtl-ordering: logical;
-webkit-svg-shadow: none;
-webkit-tap-highlight-color: rgba(0,0.180392);
-webkit-text-combine: none;
-webkit-text-decorations-in-effect: none;
-webkit-text-emphasis-color: rgb(51,51);
-webkit-text-emphasis-position: over;
-webkit-text-emphasis-style: none;
-webkit-text-fill-color: rgb(51,51);
-webkit-text-orientation: vertical-right;
-webkit-text-security: none;
-webkit-text-stroke-color: rgb(51,51);
-webkit-text-stroke-width: 0px;
-webkit-transform: none;
-webkit-transform-origin: 585px 196px;
-webkit-transform-style: flat;
-webkit-transition-delay: 0s;
-webkit-transition-duration: 0s;
-webkit-transition-property: all;
-webkit-transition-timing-function: ease;
-webkit-user-drag: auto;
-webkit-user-modify: read-only;
-webkit-user-select: text;
-webkit-writing-mode: horizontal-tb;
align-content: stretch;
align-items: stretch;
align-self: stretch;
alignment-baseline: auto;
background-attachment: scroll;
background-clip: border-Box;
background-color: rgba(0,0);
background-image: none;
background-origin: padding-Box;
background-position: 0% 0%;
background-repeat: repeat;
background-size: auto;
baseline-shift: baseline;
border-bottom-color: rgb(51,51);
border-bottom-left-radius: 0px;
border-bottom-right-radius: 0px;
border-bottom-style: none;
border-bottom-width: 0px;
border-collapse: separate;
border-image-outset: 0px;
border-image-repeat: stretch;
border-image-slice: 100%;
border-image-source: none;
border-image-width: 1;
border-left-color: rgb(51,51);
border-left-style: none;
border-left-width: 0px;
border-right-color: rgb(51,51);
border-right-style: none;
border-right-width: 0px;
border-top-color: rgb(51,51);
border-top-left-radius: 0px;
border-top-right-radius: 0px;
border-top-style: none;
border-top-width: 0px;
bottom: auto;
Box-shadow: none;
Box-sizing: content-Box;
buffered-rendering: auto;
caption-side: top;
clear: none;
clip: auto;
clip-path: none;
clip-rule: nonzero;
color: rgb(51,51);
color-interpolation: srgb;
color-interpolation-filters: linearrgb;
color-rendering: auto;
cursor: auto;
direction: ltr;
display: block;
dominant-baseline: auto;
empty-cells: show;
fill: #000000;
fill-opacity: 1;
fill-rule: nonzero;
filter: none;
flex-basis: auto;
flex-direction: row;
flex-grow: 0;
flex-shrink: 1;
flex-wrap: nowrap;
float: none;
flood-color: rgb(0,0);
flood-opacity: 1;
font-family: 'Helvetica Neue',Helvetica,Arial,sans-serif;
font-size: 14px;
font-style: normal;
font-variant: normal;
font-weight: normal;
glyph-orientation-horizontal: 0deg;
glyph-orientation-vertical: auto;
height: 392px;
image-rendering: auto;
justify-content: flex-start;
kerning: 0;
left: auto;
letter-spacing: normal;
lighting-color: rgb(255,255,255);
line-height: 20px;
list-style-image: none;
list-style-position: outside;
list-style-type: disc;
margin-bottom: 0px;
margin-left: 367.5px;
margin-right: 367.5px;
margin-top: 0px;
marker-end: none;
marker-mid: none;
marker-start: none;
mask: none;
mask-type: luminance;
max-height: none;
max-width: none;
min-height: 0px;
min-width: 0px;
opacity: 1;
order: 0;
orphans: auto;
outline-color: rgb(51,51);
outline-offset: 0px;
outline-style: none;
outline-width: 0px;
overflow-wrap: normal;
overflow-x: visible;
overflow-y: visible;
padding-bottom: 0px;
padding-left: 0px;
padding-right: 0px;
padding-top: 0px;
page-break-after: auto;
page-break-before: auto;
page-break-inside: auto;
pointer-events: auto;
position: static;
resize: none;
right: auto;
shape-rendering: auto;
speak: normal;
stop-color: rgb(0,0);
stop-opacity: 1;
stroke: none;
stroke-dasharray: none;
stroke-dashoffset: 0;
stroke-linecap: butt;
stroke-linejoin: miter;
stroke-miterlimit: 4;
stroke-opacity: 1;
stroke-width: 1;
tab-size: 8;
table-layout: auto;
text-align: start;
text-anchor: start;
text-decoration: none;
text-indent: 0px;
text-overflow: clip;
text-rendering: auto;
text-shadow: none;
text-transform: none;
top: auto;
transition-delay: 0s;
transition-duration: 0s;
transition-property: all;
transition-timing-function: ease;
unicode-bidi: normal;
vector-effect: none;
vertical-align: baseline;
visibility: visible;
white-space: normal;
widows: auto;
width: 1170px;
word-break: normal;
word-spacing: 0px;
word-wrap: normal;
writing-mode: lr-tb;
z-index: auto;
zoom: 1;