为弹出窗口设置expire cookie

Question

我想为弹出窗口设置一个过期cookie。我已将我的HTML插入到这篇文章中，并且还包含了我的CodePen，如果有帮助的话。

Cookie最多可在3个月后过期，除非用户删除其Cookie。

我不打算使用jQuery，我正在寻找纯JavaScript或CSS解决方案。

如果cookie存在，我不想为我的弹出窗口运行代码。如果它不存在，我想为我的弹出窗口运行代码，然后设置cookie。

http://codepen.io/anon/pen/rVXQaE

谢谢。

/* style link popup */
a.popup-link {
padding:17px 0;
text-align: center;
margin:10% auto;
position: relative;
width: 300px;
color: #fff;
text-decoration: none;
background-color: #FFBA00;
border-radius: 3px;
box-shadow: 0 5px 0px 0px #eea900;
display: block;
}
a.popup-link:hover {
background-color: #ff9900;
box-shadow: 0 3px 0px 0px #eea900;
-webkit-transition:all 1s;
transition:all 1s;
}
/* end link popup*/
/* animasi popup */@-webkit-keyframes autopopup {
from {opacity: 0;margin-top:-200px;}
to {opacity: 1;}
}
@-moz-keyframes autopopup {
from {opacity: 0;margin-top:-200px;}
to {opacity: 1;}
}
@keyframes autopopup {
from {opacity: 0;margin-top:-200px;}
to {opacity: 1;}
}
/* end animasi popup */
/*style popup */
#popup {
z-index:9999;
background-color: rgba(0,0,0,0.7);
position: fixed;
top:0;
left:0;
right:0;
bottom:0;
margin:0;
-webkit-animation:autopopup 2s;
-moz-animation:autopopup 2s;
animation:autopopup 2s;
}
#popup:target {
-webkit-transition:all 1s;
-moz-transition:all 1s;
transition:all 1s;
opacity: 0;
visibility: hidden;
}@media (min-width: 768px){
.popup-container {
width:600px;
}
}
@media (max-width: 767px){
.popup-container {
width:100%;
}
}
.popup-container {
position: relative;
margin:7% auto;
padding:30px 50px;
background-color: #fafafa;
color:#333;
border-radius: 3px;
}a.popup-close {
position: absolute;
top:3px;
right:3px;
background-color: #333;
padding:7px 10px;
font-size: 20px;
text-decoration: none;
line-height: 1;
color:#fff;
}
/* end style popup *//* style isi popup */
.popup-form {
margin:10px auto;
}
.popup-form h2 {
margin-bottom: 5px;
font-size: 37px;
text-transform: uppercase;
}
.popup-form .input-group {
margin:10px auto;
}
.popup-form .input-group input {
padding:17px;
text-align: center;
margin-bottom: 10px;
border-radius:3px;
font-size: 16px;
display: block;
width: 100%;
}
.popup-form .input-group input:focus {
outline-color:#FB8833;
}
.popup-form .input-group input[type="email"] {
border:0px;
position: relative;
}
.popup-form .input-group input[type="submit"] {
background-color: #FB8833;
color: #fff;
border: 0;
cursor: pointer;
}
.popup-form .input-group input[type="submit"]:focus {
box-shadow: inset 0 3px 7px 3px #ea7722;
}
/* end style isi popup */

<div class="popup-wrapper" id="popup">
<div class="popup-container"><!-- Popup Contents, just modify with your own -->
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<div class="input-group">
</div>
<!-- Popup contents is until here--><a class="popup-close" href="#popup">X</a>
</div>
</div>