<div id="center-text">
    <h2>ChatBox UI</h2>
    <p>Message send and scroll to bottom enabled </p>
  </div>
<div id="body"> 
  
<div id="chat-circle" class="btn btn-raised">
        <div id="chat-overlay"></div>
		    <i class="material-icons">speaker_phone</i>
	</div>
  
  <div class="chat-box">
    <div class="chat-box-header">
      ChatBot
      <span class="chat-box-toggle"><i class="material-icons">close</i></span>
    </div>
    <div class="chat-box-body">
      <div class="chat-box-overlay">   
      </div>
      <div class="chat-logs">
       
      </div><!--chat-log -->
    </div>
    <div class="chat-input">      
      <form>
        <input type="text" id="chat-input" placeholder="Send a message..."/>
      <button type="submit" class="chat-submit" id="chat-submit"><i class="material-icons">send</i></button>
      </form>      
    </div>
  </div>
  
  
  
  
</div>
html, body {
  background: #efefef;      
  height:100%;  
}
#center-text {          
  display: flex;
  flex: 1;
  flex-direction:column; 
  justify-content: center;
  align-items: center;  
  height:100%;
  
}
#chat-circle {
  position: fixed;
  bottom: 50px;
  right: 50px;
  background: #5A5EB9;
  width: 80px;
  height: 80px;  
  border-radius: 50%;
  color: white;
  padding: 28px;
  cursor: pointer;
  box-shadow: 0px 3px 16px 0px rgba(0, 0, 0, 0.6), 0 3px 1px -2px rgba(0, 0, 0, 0.2), 0 1px 5px 0 rgba(0, 0, 0, 0.12);
}

.btn#my-btn {
     background: white;
    padding-top: 13px;
    padding-bottom: 12px;
    border-radius: 45px;
    padding-right: 40px;
    padding-left: 40px;
    color: #5865C3;
}
#chat-overlay {
    background: rgba(255,255,255,0.1);
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border-radius: 50%;
    display: none;
}


.chat-box {
  display:none;
  background: #efefef;
  position:fixed;
  right:30px;
  bottom:50px;  
  width:350px;
  max-width: 85vw;
  max-height:100vh;
  border-radius:5px;  
/*   box-shadow: 0px 5px 35px 9px #464a92; */
  box-shadow: 0px 5px 35px 9px #ccc;
}
.chat-box-toggle {
  float:right;
  margin-right:15px;
  cursor:pointer;
}
.chat-box-header {
  background: #5A5EB9;
  height:70px;
  border-top-left-radius:5px;
  border-top-right-radius:5px; 
  color:white;
  text-align:center;
  font-size:20px;
  padding-top:17px;
}
.chat-box-body {
  position: relative;  
  height:370px;  
  height:auto;
  border:1px solid #ccc;  
  overflow: hidden;
}
.chat-box-body:after {
  content: "";
  background-image: url('data:image/svg+xml;base64,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');
  opacity: 0.1;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  height:100%;
  position: absolute;
  z-index: -1;   
}
#chat-input {
  background: #f4f7f9;
  width:100%; 
  position:relative;
  height:47px;  
  padding-top:10px;
  padding-right:50px;
  padding-bottom:10px;
  padding-left:15px;
  border:none;
  resize:none;
  outline:none;
  border:1px solid #ccc;
  color:#888;
  border-top:none;
  border-bottom-right-radius:5px;
  border-bottom-left-radius:5px;
  overflow:hidden;  
}
.chat-input > form {
    margin-bottom: 0;
}
#chat-input::-webkit-input-placeholder { /* Chrome/Opera/Safari */
  color: #ccc;
}
#chat-input::-moz-placeholder { /* Firefox 19+ */
  color: #ccc;
}
#chat-input:-ms-input-placeholder { /* IE 10+ */
  color: #ccc;
}
#chat-input:-moz-placeholder { /* Firefox 18- */
  color: #ccc;
}
.chat-submit {  
  position:absolute;
  bottom:3px;
  right:10px;
  background: transparent;
  box-shadow:none;
  border:none;
  border-radius:50%;
  color:#5A5EB9;
  width:35px;
  height:35px;  
}
.chat-logs {
  padding:15px; 
  height:370px;
  overflow-y:scroll;
}

@media only screen and (max-width: 500px) {
   .chat-logs {
        height:40vh;
    }
}

.chat-msg.user > .msg-avatar img {
  width:45px;
  height:45px;
  border-radius:50%;
  float:left;
  width:15%;
}
.chat-msg.self > .msg-avatar img {
  width:45px;
  height:45px;
  border-radius:50%;
  float:right;
  width:15%;
}
.cm-msg-text {
  background:white;
  padding:10px 15px 10px 15px;  
  color:#666;
  max-width:75%;
  float:left;
  margin-left:10px; 
  position:relative;
  margin-bottom:20px;
  border-radius:30px;
}
.chat-msg {
  clear:both;    
}
.chat-msg.self > .cm-msg-text {  
  float:right;
  margin-right:10px;
  background: #5A5EB9;
  color:white;
}
.cm-msg-button>ul>li {
  list-style:none;
  float:left;
  width:50%;
}
.cm-msg-button {
    clear: both;
    margin-bottom: 70px;
}
$(function() {
  var INDEX = 0;
  $("#chat-submit").click(function(e) {
    e.preventDefault();
    var msg = $("#chat-input").val(); 
    if(msg.trim() == ''){
      return false;
    }
    generate_message(msg, 'self');
    var buttons = [
        {
          name: 'Existing User',
          value: 'existing'
        },
        {
          name: 'New User',
          value: 'new'
        }
      ];
    setTimeout(function() {      
      generate_message(msg, 'user');  
    }, 1000)
    
  })
  
  function generate_message(msg, type) {
    INDEX++;
    var str="";
    str += "<div id='cm-msg-"+INDEX+"' class=\"chat-msg "+type+"\">";
    str += "          <span class=\"msg-avatar\">";
    str += "            <img src=\"https:\/\/image.crisp.im\/avatar\/operator\/196af8cc-f6ad-4ef7-afd1-c45d5231387c\/240\/?1483361727745\">";
    str += "          <\/span>";
    str += "          <div class=\"cm-msg-text\">";
    str += msg;
    str += "          <\/div>";
    str += "        <\/div>";
    $(".chat-logs").append(str);
    $("#cm-msg-"+INDEX).hide().fadeIn(300);
    if(type == 'self'){
     $("#chat-input").val(''); 
    }    
    $(".chat-logs").stop().animate({ scrollTop: $(".chat-logs")[0].scrollHeight}, 1000);    
  }  
  
  function generate_button_message(msg, buttons){    
    /* Buttons should be object array 
      [
        {
          name: 'Existing User',
          value: 'existing'
        },
        {
          name: 'New User',
          value: 'new'
        }
      ]
    */
    INDEX++;
    var btn_obj = buttons.map(function(button) {
       return  "              <li class=\"button\"><a href=\"javascript:;\" class=\"btn btn-primary chat-btn\" chat-value=\""+button.value+"\">"+button.name+"<\/a><\/li>";
    }).join('');
    var str="";
    str += "<div id='cm-msg-"+INDEX+"' class=\"chat-msg user\">";
    str += "          <span class=\"msg-avatar\">";
    str += "            <img src=\"https:\/\/image.crisp.im\/avatar\/operator\/196af8cc-f6ad-4ef7-afd1-c45d5231387c\/240\/?1483361727745\">";
    str += "          <\/span>";
    str += "          <div class=\"cm-msg-text\">";
    str += msg;
    str += "          <\/div>";
    str += "          <div class=\"cm-msg-button\">";
    str += "            <ul>";   
    str += btn_obj;
    str += "            <\/ul>";
    str += "          <\/div>";
    str += "        <\/div>";
    $(".chat-logs").append(str);
    $("#cm-msg-"+INDEX).hide().fadeIn(300);   
    $(".chat-logs").stop().animate({ scrollTop: $(".chat-logs")[0].scrollHeight}, 1000);
    $("#chat-input").attr("disabled", true);
  }
  
  $(document).delegate(".chat-btn", "click", function() {
    var value = $(this).attr("chat-value");
    var name = $(this).html();
    $("#chat-input").attr("disabled", false);
    generate_message(name, 'self');
  })
  
  $("#chat-circle").click(function() {    
    $("#chat-circle").toggle('scale');
    $(".chat-box").toggle('scale');
  })
  
  $(".chat-box-toggle").click(function() {
    $("#chat-circle").toggle('scale');
    $(".chat-box").toggle('scale');
  })
  
})

External CSS

  1. https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.0.0-alpha.6/css/bootstrap.min.css
  2. https://cdnjs.cloudflare.com/ajax/libs/bootstrap-material-design/4.0.2/bootstrap-material-design.css
  3. https://fonts.googleapis.com/icon?family=Material+Icons

External JavaScript

  1. https://cdnjs.cloudflare.com/ajax/libs/jquery/3.1.1/jquery.min.js
  2. https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.0.0-alpha.6/js/bootstrap.min.js