What are the cookie attributes provided by JavaScript?

The cookie attributes provided by JavaScript include: expires attribute (declaring the expiration time of the cookie), max-age attribute (declaring the maximum time of cookie activity), domain attribute (defining a valid domain name), and path attribute.

What is Cookie?

Cookies are a large amount of information that persists between the server and the client. The web browser will store this information while browsing.

Cookies usually contain information as a string in the form of a semicolon-separated name-value pair; it maintains the user's status and remembers user information in web pages.

How to create cookies in JavaScript?

In JavaScript, we can create, read, update and delete cookies using the document.cookie property.

Basic syntax for creating cookies:

document.cookie = “name = value” ;

JavaScript's Cookie attributes

JavaScript provides some optional attributes to enhance The functions of cookies, let’s take a look at these attributes:

expires attribute:

can maintain the status of the cookie until the specified date and time; that is, it Declaring a date and time that represents the duration of the cookie's activity is one of the ways to create a persistent cookie.

Example: Set the validity period of the cookie for "username = php Chinese website" to 2030, August 20, 12:00:00

document.cookie = “username = php中文网; expires = Sun，20 Aug 2030 12:00:00 UTC” ;

Note: expires attribute, once declared If the time is in the past (any time in the past will do), the cookie will be automatically deleted; it is also a way to delete cookies.

Example: Set the validity period to 1970, January 1, 00:00:00

document.cookie = "username=php中文网; expires= Thu, 01 Jan 1970 00:00:00 GMT";

max-age attribute

The status of the cookie can be maintained for a specified time, which is calculated in seconds. It is also one of the ways to create persistent cookies.

document.cookie = "username =php中文网; max-age ="  +（60 * 60 * 24 * 365）+";"

Note: Cookies can also be deleted using the max-age attribute. You only need to provide zero or a negative number (indicating the number of seconds) to the max-age attribute.

 document.cookie = "name = php中文网; max-age = 0" ;

domain attribute

It is used to specify the domain in which the cookie is valid; the cookie will be valid only in the specified domain name.

Suppose we provide any domain name for the domain attribute, for example:

domain = php .cn

Here, the cookie is valid for the given domain and all its subdomains.

But, if we provide any subdomain to the attribute, for example:

domain=img.php .cn

Here, the cookie will be valid only for the given subdomain. Therefore, it is a better method to provide the cookie with a domain name rather than a subdomain name to make the cookie valid under the specified domain name.

path attribute: Extend the scope of the cookie to all pages of the website

Simple example of JavaScript Cookie

Example: JavaScript creates Cookie, gets Cookie, reads Cookie

<script>
function setCookie(cname,cvalue,exdays){
	var d = new Date();
	d.setTime(d.getTime()+(exdays*24*60*60*1000));
	var expires = "expires="+d.toGMTString();
	document.cookie = cname+"="+cvalue+"; "+expires;
}
function getCookie(cname){
	var name = cname + "=";
	var ca = document.cookie.split(&#39;;&#39;);
	for(var i=0; i<ca.length; i++) {
		var c = ca[i].trim();
		if (c.indexOf(name)==0) { return c.substring(name.length,c.length); }
	}
	return "";
}
function checkCookie(){
	var user=getCookie("username");
	if (user!=""){
		alert("欢迎 " + user + " 再次访问");
	}
	else {
		user = prompt("请输入你的名字:","");
  		if (user!="" && user!=null){
    		setCookie("username",user,30);
    	}
	}
}
</script>

Rendering:

When entering the name, press the "OK" button Afterwards, refresh the current page, and it will appear:

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