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JavaScript cookie usage (concept, setting, reading and deletion)

高洛峰Original: 2017-01-18 13:20:321305browse

The examples in this article describe the usage of javascript cookie. Share it with everyone for your reference, the details are as follows:

1. What is a cookie?

Cookies are used by pages to save information, such as automatic login, remembering user names, etc.

2. Characteristics of cookies

All pages in the same website share a set of cookies

Cookies have quantity and size restrictions

Cookies have expiration time

3. How to use cookies?

Write cookies through document.cookie

<!DOCTYPE HTML>
<html>
<head>
 <meta charset="UTF-8">
 <title>cookie基础</title>
</head>
<body>
</body>
</html>
<script type="text/javascript">
document.cookie = &#39;username=abc&#39;;
document.cookie = &#39;password=123&#39;;
document.cookie = &#39;email=abcdef@123.com&#39;;
</script>

Open the browser to view cookies, you can find that the newly defined cookies will not overwrite the original ones.

If no expiration time is set, closing the browser will clear the cookie. How to set the expiration time? The answer is: expires. Generally we will use it in conjunction with Date objects.

var d = new Date();
d.setTime(d.getTime() + 1 * 3600 * 1000);
document.cookie = &#39;username=abc; expires=&#39; + d.toGMTString();

We can see through the Firefox browser that the expiration time of username is 1 hour after the current time.

Finally encapsulate the method of obtaining cookies:

function setCookie(name,value,hours){ 
 var d = new Date();
 d.setTime(d.getTime() + hours * 3600 * 1000);
 document.cookie = name + &#39;=&#39; + value + &#39;; expires=&#39; + d.toGMTString();
}

Now that we have learned how to set cookies, how do we read cookies?

First, let’s take a look at what type of content is in the cookie?

document.cookie = &#39;username=abc&#39;;
document.cookie = &#39;password=123&#39;;
document.cookie = &#39;email=abcdef@123.com&#39;;
typeof document.cookie; //string
alert(document.cookie); //&#39;username=abc; password=123; email=abcdef@123.com&#39;

What you get is a string. It should be noted that there is a space after each ;.

So how do we get the specific value? Attached code:

function getCookie(name){ 
 var arr = document.cookie.split(&#39;; &#39;);
 for(var i = 0; i < arr.length; i++){
 var temp = arr[i].split(&#39;=&#39;);
 if(temp[0] == name){
  return temp[1];
 }
 }
 return &#39;&#39;;
}

In addition to setting and getting cookies, we can also delete cookies. We often see functions like clearing usernames on the Internet, which actually use clearing cookies.

Clearing cookies is actually very simple, just set the expiration time to the past time.

function removeCookie(name){
 var d = new Date();
 d.setTime(d.getTime() - 10000);
 document.cookie = name + &#39;=1; expires=&#39; + d.toGMTString();
}

Finally we will encapsulate setting, obtaining and clearing cookies into a cookie.js

##1234567891011121314151617181920 function setCookie(name,value,hours){ var d = new Date(); d.setTime(d.getTime() + hours * 3600 * 1000); document.cookie = name + '=' + value + '; expires=' + d.toGMTString();}function getCookie(name ){ var arr = document.cookie.split('; '); for(var i = 0; i < arr.length; i++){ var temp = arr[i].split('='); if( temp[0] == name){ return temp[1]; } } return '';}function removeCookie(name){ var d = new Date(); d.setTime(d.getTime() - 10000); document .cookie = name + '=1; expires=' + d.toGMTString();}

I hope this article will be helpful to everyone in JavaScript programming.

For more basic tutorials on javascript cookie usage (concepts, settings, reading and deletion), please pay attention to the PHP Chinese website!

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