changing css class and a jquery function when it reaches a div
<p>I want to change a class from "class A" to "Class B" when it reaches DIV of "Class A" to "Class B"..</p>

<p>Here is the thing what I want, I have push menu when hamburger icon. The icon is generally in white background with black box shadow. My whole website background is dark. So it is perfect for dark background. </p>

<p>But I have few DIVs which are in white, when I reach that white DIV my menu is hardly visible.</p>

<p>So my question is I want to change the class of my menu from white to black when it reaches white background div. And I want to change the function of that menu as well in jquery. Because I have a "click" function to expand the menu.</p>

<p>Here is the HTML:</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>$('.nav-trigger').on('click', function() {
    $(this).toggleClass('on');
    $('.nav-menu').fadeToggle(200);
});</code></pre>
<pre class="snippet-code-css lang-css prettyprint-override"><code>* {
  box-sizing: border-box;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
}

*, *:before, *:after {
  box-sizing: inherit;
}

html {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Advent Pro", sans-serif;
  overflow-x: hidden;
}

section {
  width: 100%;
  padding: 0 7%;
  display: table;
  margin: 0;
  max-width: none;
  background-color: #23222a;
  height: 100vh;
  color: #fff;
}

.content {
  display: table-cell;
  vertical-align: middle;
  color: #fff;
}

.nav-trigger {
  width: 30px;
  height: 30px;
  position: fixed;
  top: 10px;
  right: 10px;
  z-index: 20;
  cursor: pointer;
  -webkit-transition: top .1s ease-in-out;
  transition: top .1s ease-in-out;
}
.nav-trigger span {
  display: block;
  width: 100%;
  height: 2px;
  background: #fff;
  margin: 7px auto;
  -webkit-transition: all 0.3s ease-in-out;
  transition: all 0.3s ease-in-out;
  box-shadow: 0 0 3px 1px rgba(0, 0, 0, 0.3);
}
.nav-trigger span:first-child {
  top: 0;
  left: 0;
}
.nav-trigger span:nth-child(2) {
  width: 20px;
  top: 10px;
  left: 0;
}
.nav-trigger span:last-child {
  top: 20px;
  left: 0;
}
.nav-trigger .on {
  top: 10px;
}

.nav-trigger.on span:first-child {
  -webkit-transform: translateY(10px) rotate(45deg);
  transform: translateY(10px) rotate(45deg);
}

.nav-trigger.on span:nth-child(2) {
  -webkit-transform: translateX(50px);
  transform: translateX(50px);
  opacity: 0;
}

.nav-trigger.on span:last-child {
  -webkit-transform: translateY(-8px) rotate(-45deg);
  transform: translateY(-8px) rotate(-45deg);
}

.nav-trigger-dark {
  width: 30px;
  height: 30px;
  position: fixed;
  top: 10px;
  right: 10px;
  z-index: 20;
  cursor: pointer;
  -webkit-transition: top .1s ease-in-out;
  transition: top .1s ease-in-out;
}
.nav-trigger-dark span {
  display: block;
  width: 100%;
  height: 2px;
  background: #000;
  margin: 7px auto;
  -webkit-transition: all 0.3s ease-in-out;
  transition: all 0.3s ease-in-out;
  box-shadow: 0 0 3px 1px rgba(255, 255, 255, 0.3);
}
.nav-trigger-dark span:first-child {
  top: 0;
  left: 0;
}
.nav-trigger-dark span:nth-child(2) {
  width: 20px;
  top: 10px;
  left: 0;
}
.nav-trigger-dark span:last-child {
  top: 20px;
  left: 0;
}
.nav-trigger-dark .on {
  top: 10px;
}

.nav-trigger-dark.on span:first-child {
  -webkit-transform: translateY(10px) rotate(45deg);
  transform: translateY(10px) rotate(45deg);
}

.nav-trigger-dark.on span:nth-child(2) {
  -webkit-transform: translateX(50px);
  transform: translateX(50px);
  opacity: 0;
}

.nav-trigger-dark.on span:last-child {
  -webkit-transform: translateY(-8px) rotate(-45deg);
  transform: translateY(-8px) rotate(-45deg);
}

.nav-menu {
  height: 100%;
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  display: none;
  z-index: 19;
  overflow: hidden;
}
.nav-menu ul {
  list-style-type: none;
  padding: 0;
  margin: 0;
  width: 100%;
  max-width: 100%;
  text-align: center;
  position: relative;
  -webkit-transition: opacity .35s, visibility .35s, height .35s;
  transition: opacity .35s, visibility .35s, height .35s;
}
.nav-menu ul a {
  position: relative;
  float: left;
  margin: 0;
  width: 25%;
  height: 100vh;
  text-align: center;
  cursor: pointer;
  background: #e65454;
  color: #fff;
  text-decoration: none;
}
@media (max-width: 30em) {
  .nav-menu ul a {
    width: 100%;
    height: 25vh;
  }
}
.nav-menu ul a li {
  position: absolute;
  text-transform: uppercase;
  font-family: "Advent Pro", sans-serif;
  top: 45%;
  left: 0;
  position: relative;
  -webkit-animation: fadeInRight .5s ease forwards;
  animation: fadeInRight .5s ease forwards;
}
@media (max-width: 30em) {
  .nav-menu ul a li {
    top: 25%;
  }
}
.nav-menu ul a h2.mb {
  -webkit-transition: -webkit-transform 0.35s;
  transition: -webkit-transform 0.35s;
  transition: transform 0.35s;
  transition: transform 0.35s, -webkit-transform 0.35s;
  margin-bottom: -20px;
  font-size: 2.25rem;
  /* 36/16 */
}
@media (max-width: 30em) {
  .nav-menu ul a h2.mb {
    font-size: 1.688rem;
    /* 27/16 */
  }
}
@media (min-width: 48em) and (max-width: 61.9375em) {
  .nav-menu ul a h2.mb {
    font-size: 2rem;
    /* 32/16 */
    margin-bottom: -13px;
  }
}
.nav-menu ul a h2.mt {
  -webkit-transition: -webkit-transform 0.35s;
  transition: -webkit-transform 0.35s;
  transition: transform 0.35s;
  transition: transform 0.35s, -webkit-transform 0.35s;
  margin-bottom: -73px;
  font-size: 2.25rem;
  /* 36/16 */
}
@media (max-width: 30em) {
  .nav-menu ul a h2.mt {
    font-size: 1.688rem;
    /* 27/16 */
  }
}
@media (min-width: 48em) and (max-width: 61.9375em) {
  .nav-menu ul a h2.mt {
    font-size: 2rem;
    /* 32/16 */
  }
}
.nav-menu ul a i {
  font-style: normal;
  opacity: 0;
  -webkit-transition: opacity 0.35s, -webkit-transform 0.35s;
  transition: opacity 0.35s, -webkit-transform 0.35s;
  transition: opacity 0.35s, transform 0.35s;
  transition: opacity 0.35s, transform 0.35s, -webkit-transform 0.35s;
  -webkit-transform: translate3d(0, -30px, 0);
  transform: translate3d(0, -30px, 0);
  font-size: 1.875rem;
  /* 30/16 */
}
@media (max-width: 30em) {
  .nav-menu ul a i {
    display: none;
  }
}
.nav-menu ul a:hover {
  background: #fff;
  color: #e65454;
}
.nav-menu ul a:hover h2 {
  -webkit-transform: translate3d(0, 0, 0);
  transform: translate3d(0, 0, 0);
}
.nav-menu ul a:hover i {
  opacity: 1;
  -webkit-transform: translate3d(0, 0, 0);
  transform: translate3d(0, 0, 0);
}
.nav-menu ul a.active {
  background: #fff;
  color: #e65454;
}
.nav-menu ul a.active:hover {
  color: #000;
}

@-webkit-keyframes fadeInRight {
  0% {
    opacity: 0;
    left: 20%;
  }
  100% {
    opacity: 1;
    left: 0;
  }
}
@keyframes fadeInRight {
  0% {
    opacity: 0;
    left: 20%;
  }
  100% {
    opacity: 1;
    left: 0;
  }
}
.bgwhite {
  background: #fff;
}</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"&gt;&lt;/script&gt;

&lt;div class="nav-trigger"&gt;
   &lt;span&gt;&lt;/span&gt;&lt;span&gt;&lt;/span&gt;&lt;span&gt;&lt;/span&gt;
  &lt;/div&gt;
  &lt;div class="nav-menu"&gt;
   &lt;ul&gt;
    &lt;a href="#"&gt; &lt;li&gt;&lt;h2 class="mt"&gt;Home&lt;/h2&gt;&lt;i&gt;Go to&lt;/i&gt;&lt;/li&gt;&lt;/a&gt;
    &lt;a href="#"&gt;&lt;li&gt;&lt;h2 class="mb"&gt;About&lt;/h2&gt;&lt;i&gt;Me&lt;/i&gt;&lt;/li&gt;&lt;/a&gt;
    &lt;a href="#"&gt;&lt;li&gt;&lt;h2 class="mt"&gt;Work&lt;/h2&gt;&lt;i&gt;My&lt;/i&gt;&lt;/li&gt;&lt;/a&gt;
    &lt;a href="#"&gt;&lt;li&gt;&lt;h2 class="mb"&gt;Contact&lt;/h2&gt;&lt;i&gt;Me&lt;/i&gt;&lt;/li&gt;&lt;/a&gt;
   &lt;/ul&gt;
  &lt;/div&gt;
&lt;section&gt;
  &lt;div class="content"&gt;
    
    &lt;/div&gt;
  &lt;/section&gt;
&lt;section class="bgwhite"&gt;
  &lt;div class="content"&gt;
    
    &lt;/div&gt;
  &lt;/section&gt;</code></pre>
</div>
</div>
</p>

<p>as you can see in the snippit above when i reach the white background section, my hamburger menu trigger is hardly visible..</p>

<p>I have a css class with dark menu in the name of "nav-trigger dark".</p>

<p>Now I want to change that "nav-trigger" class to "nav-trigger-dark" class in that html and in that jquery script as well.</p>