How to delete a cookie?

Is my function of creating a cookie correct? How do I delete the cookie at the beginning of my program? is there a simple coding?

function createCookie(name,value,days)

function setCookie(c_name,value,1) {
  document.cookie = c_name + "=" +escape(value);
}

setCookie('cookie_name',mac);

function eraseCookie(c_name) {
  createCookie(cookie_name,"",-1);
}

Try this:

function delete_cookie( name, path, domain ) {
  if( get_cookie( name ) ) {
    document.cookie = name + "=" +
      ((path) ? ";path="+path:"")+
      ((domain)?";domain="+domain:"") +
      ";expires=Thu, 01 Jan 1970 00:00:01 GMT";
  }
}

You can define get_cookie() like this:

function get_cookie(name){
    return document.cookie.split(';').some(c => {
        return c.trim().startsWith(name + '=');
    });
}

Here a good link on Quirksmode.

function setCookie(name,value,days) {
	var expires = "";
	if (days) {
		var date = new Date();
		date.setTime(date.getTime() + (days*24*60*60*1000));
		expires = "; expires=" + date.toUTCString();
	}
	document.cookie = name + "=" + (value || "")  + expires + "; path=/";
}
function getCookie(name) {
	var nameEQ = name + "=";
	var ca = document.cookie.split(';');
	for(var i=0;i < ca.length;i++) {
		var c = ca[i];
		while (c.charAt(0)==' ') c = c.substring(1,c.length);
		if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
	}
	return null;
}
function eraseCookie(name) {   
	document.cookie = name+'=; Max-Age=-99999999;';  
}

would this work?

function eraseCookie(name) {
    document.cookie = name + '=; Max-Age=0'
}

I know Max-Age causes the cookie to be a session cookie in IE when creating the cookie. Not sure how it works when deleting cookies.

Some of the other solutions might not work if you created the cookie manually.

Here's a quick way to delete a cookie:

document.cookie = 'COOKIE_NAME=; Max-Age=0; path=/; domain=' + location.host;

If this doesn't work, try replacing location.host with location.hostname in the snippet above.

Here is an implementation of a delete cookie function with unicode support from Mozilla:

function removeItem(sKey, sPath, sDomain) {
    document.cookie = encodeURIComponent(sKey) + 
                  "=; expires=Thu, 01 Jan 1970 00:00:00 GMT" + 
                  (sDomain ? "; domain=" + sDomain : "") + 
                  (sPath ? "; path=" + sPath : "");
}

removeItem("cookieName");

If you use AngularJs, try $cookies.remove (underneath it uses a similar approach):

$cookies.remove('cookieName');

You can do this by setting the date of expiry to yesterday.

Setting it to "-1" doesn't work. That marks a cookie as a Sessioncookie.

To delete a cookie I set it again with an empty value and expiring in 1 second. In details, I always use one of the following flavours (I tend to prefer the second one):

1.

	function setCookie(key, value, expireDays, expireHours, expireMinutes, expireSeconds) {
		var expireDate = new Date();
		if (expireDays) {
			expireDate.setDate(expireDate.getDate() + expireDays);
		}
		if (expireHours) {
			expireDate.setHours(expireDate.getHours() + expireHours);
		}
		if (expireMinutes) {
			expireDate.setMinutes(expireDate.getMinutes() + expireMinutes);
		}
		if (expireSeconds) {
			expireDate.setSeconds(expireDate.getSeconds() + expireSeconds);
		}
		document.cookie = key +"="+ escape(value) +
			";domain="+ window.location.hostname +
			";path=/"+
			";expires="+expireDate.toUTCString();
	}

	function deleteCookie(name) {
		setCookie(name, "", null , null , null, 1);
	}

Usage:

setCookie("reminder", "buyCoffee", null, null, 20);
deleteCookie("reminder");

2

	function setCookie(params) {
		var name			= params.name,
			value			= params.value,
			expireDays		= params.days,
			expireHours		= params.hours,
			expireMinutes	= params.minutes,
			expireSeconds	= params.seconds;

		var expireDate = new Date();
		if (expireDays) {
			expireDate.setDate(expireDate.getDate() + expireDays);
		}
		if (expireHours) {
			expireDate.setHours(expireDate.getHours() + expireHours);
		}
		if (expireMinutes) {
			expireDate.setMinutes(expireDate.getMinutes() + expireMinutes);
		}
		if (expireSeconds) {
			expireDate.setSeconds(expireDate.getSeconds() + expireSeconds);
		}

		document.cookie = name +"="+ escape(value) +
			";domain="+ window.location.hostname +
			";path=/"+
			";expires="+expireDate.toUTCString();
	}

	function deleteCookie(name) {
		setCookie({name: name, value: "", seconds: 1});
	}

Usage:

setCookie({name: "reminder", value: "buyCoffee", minutes: 20});
deleteCookie("reminder");

I had trouble deleting a cookie made via JavaScript and after I added the host it worked (scroll the code below to the right to see the location.host). After clearing the cookies on a domain try the following to see the results:

if (document.cookie.length==0)
{
 document.cookie = 'name=example; expires='+new Date((new Date()).valueOf()+1000*60*60*24*15)+'; path=/; domain='+location.host;

 if (document.cookie.length==0) {alert('Cookies disabled');}
 else
 {
  document.cookie = 'name=example; expires=Thu, 01 Jan 1970 00:00:00 GMT; path=/; domain='+location.host;

  if (document.cookie.length==0) {alert('Created AND deleted cookie successfully.');}
  else {alert('document.cookies.length = '+document.cookies.length);}
 }
}

For people who just want 1 line of code to delete a cookie:

If you created a cookie, for example in a web browser console with document.cookie = "test=hello"

You can delete it with:

document.cookie = "test=;expires=" + new Date(0).toUTCString()

Or if you prefer to write the UTC date directly:

document.cookie = "test=;expires=Thu, 01 Jan 1970 00:00:00 GMT"

If you are on a different path than the cookie (for example if you want to delete a cookie that is used on all paths), you can add path=/; after test=; and if you are on a different domain (for example when a cookie is set for all subdomains by using .example.com instead of www.example.com), you can add domain=.example.com; after test=;.

Update: instead of expires=..., using Max-Age=0 like in other answers works also (tested with Firefox).

I use this on my websites that works on Chrome and Firefox.

function delete_cookie(name) { document.cookie = name +'=; Path=/;  Domain=' + location.host +  '; Expires=Thu, 01 Jan 1970 00:00:01 GMT; SameSite=None; Secure' }