<div class="wrap" id="wrap">
  
  <header class="top-header">
    <span class="menu-icon">☰</span>
  </header>
  
  <div class="search">
    <input type="search" placeholder="Search or type URL" />
  </div>
  
  <div class="top">
    <div class="hero"></div>
  </div>
  
  <main>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
  </main>
  
</div>

* {
  box-sizing: border-box;
}
body {
  margin: 0;
}

.wrap {
  width: 320px;
  border: 1px solid #ccc;
  height: 480px;
  overflow: auto;
  position: relative;
}
.top-header {
  position: fixed;
  top: 0;
  left: 0;
  width: 320px;
  height: 60px;
  .menu-icon {
    position: absolute;
    top: 0;
    right: 0;
    padding: 18px 20px;
  }
  .fix-search & {
    background: #eee;
  }
}

.search {
  position: absolute;
  top: 155px;
  left: 20px;
  right: 20px;
  input {
    width: 265px;
    border: 1px solid #ccc;
    padding: 8px;
    font-size: 15px;
    transition: width 0.2s;
    -webkit-appearance: none;
  }
  .fix-search & {
    position: fixed;
    top: 10px;
    input {
      width: 250px;
    }
  }
}

.top {
  height: 250px;
  padding-top: 40px;
}
.hero {
  width: 200px;
  height: 100px;
  background: #ccc;
  margin: 0 auto;
}

main {
  padding: 0 20px;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  div {
    width: 125px;
    height: 80px;
    background: #ccc;
    margin: 0 0 20px 0;
  }
}

var wrap = $("#wrap");

wrap.on("scroll", function(e) {
    
  if (this.scrollTop > 147) {
    wrap.addClass("fix-search");
  } else {
    wrap.removeClass("fix-search");
  }
  
});