<div id="wrap">

  <!-- section -->
  <div class="section">
    <div class="center">

      <div class="content content--1"></div>
      <div class="content content--2">
        <div class="heads">
          <div class="head"><span>Title 1</span></div>
          <div class="head"><span>Title 2</span></div>
          <div class="head"><span>Title 3</span></div>
        </div>
      </div>

    </div>
  </div>
  <!--/section -->

</div>

html,
body {
  margin: 0;
  padding: 0;
  font-family: sans-serif;
  font-size: 16px;
  line-height: 1.4;
  color: #555;
  background: #fff;
}

* {
  box-sizing: border-box;
}

#wrap {
  position: relative;
}

.section {
  padding: 40px;
}

.center {
  width: 100%;
  max-width: 980px;
  margin: auto;
}

.content {
  &--1 {
    height: 1000px;
  }
  
  &--2 {
    height: 500px;
  }
}

.heads {
  display: flex;
}

.head {
  flex: 1 1 auto;
  font-size: 24px;
  position: relative;
  margin: 5px;
  
  &::before {
    content: '';
    display: block;
    position: absolute;
    bottom: 0;
    left: 0;
    height: 1px;
    width: 100%;
    background: #000;
    transform-origin: left top;
    transition: transform 1s ease;
    transform: scaleX(0);
  }
  
  &.in-viewport {
    &::before {
      transform: scaleX(1); 
    }
  }
}

function inViewport(elem, tolerance) {  
  if(elem.offset().top <= $(window).scrollTop() + $(window).height() - tolerance) {
    elem.addClass('in-viewport');
  }
}

$(window).on('load scroll', function() {
  inViewport($('.head'), 80);
});