如何检查 cookie 是否存在？

Question

What's a good way to check if a cookie exist?

Conditions:

Cookie exists if

cookie1=;cookie1=345534;
//or
cookie1=345534;cookie1=;
//or
cookie1=345534;

Cookie doesn't exist if

cookie=;
//or
<blank>

Answer 1

You can call the function getCookie with the name of the cookie you want, then check to see if it is = null.

function getCookie(name) {
    var dc = document.cookie;
    var prefix = name + "=";
    var begin = dc.indexOf("; " + prefix);
    if (begin == -1) {
        begin = dc.indexOf(prefix);
        if (begin != 0) return null;
    }
    else
    {
        begin += 2;
        var end = document.cookie.indexOf(";", begin);
        if (end == -1) {
        end = dc.length;
        }
    }
    // because unescape has been deprecated, replaced with decodeURI
    //return unescape(dc.substring(begin + prefix.length, end));
    return decodeURI(dc.substring(begin + prefix.length, end));
} 

function doSomething() {
    var myCookie = getCookie("MyCookie");

    if (myCookie == null) {
        // do cookie doesn't exist stuff;
    }
    else {
        // do cookie exists stuff
    }
}

Answer 2

I have crafted an alternative non-jQuery version:

document.cookie.match(/^(.*;)?\s*MyCookie\s*=\s*[^;]+(.*)?$/)

It only tests for cookie existence. A more complicated version can also return cookie value:

value_or_null = (document.cookie.match(/^(?:.*;)?\s*MyCookie\s*=\s*([^;]+)(?:.*)?$/)||[,null])[1]

Put your cookie name in in place of MyCookie .

Answer 3

document.cookie.indexOf('cookie_name=');

It will return -1 if that cookie does not exist.

ps Only drawback of it is (as mentioned in comments) that it will mistake if there is cookie set with such name: any_prefix_cookie_name

( Source )

Answer 4

ATTENTION! the chosen answer contains a bug (Jac's answer) .

if you have more than one cookie (very likely..) and the cookie you are retrieving is the first on the list, it doesn't set the variable "end" and therefore it will return the entire string of characters following the "cookieName=" within the document.cookie string!

here is a revised version of that function:

function getCookie( name ) {
    var dc,
        prefix,
        begin,
        end;
    
    dc = document.cookie;
    prefix = name + "=";
    begin = dc.indexOf("; " + prefix);
    end = dc.length; // default to end of the string

    // found, and not in first position
    if (begin !== -1) {
        // exclude the "; "
        begin += 2;
    } else {
        //see if cookie is in first position
        begin = dc.indexOf(prefix);
        // not found at all or found as a portion of another cookie name
        if (begin === -1 || begin !== 0 ) return null;
    } 

    // if we find a ";" somewhere after the prefix position then "end" is that position,
    // otherwise it defaults to the end of the string
    if (dc.indexOf(";", begin) !== -1) {
        end = dc.indexOf(";", begin);
    }

    return decodeURI(dc.substring(begin + prefix.length, end) ).replace(/\"/g, ''); 
}

Answer 5

This is an old question, but here's the approach I use ...

function getCookie(name) {
    var match = document.cookie.match(RegExp('(?:^|;\\s*)' + name + '=([^;]*)')); 
    return match ? match[1] : null;
}

This returns null either when the cookie doesn't exist, or when it doesn't contain the requested name.
Otherwise, the value (of the requested name) is returned.

A cookie should never exist without a value -- because, in all fairness, what's the point of that? 😄
If it's no longer needed, it's best to just get rid of it all together.

function deleteCookie(name) {
    document.cookie = name +"=; Path=/; Expires=Thu, 01 Jan 1970 00:00:01 GMT;";
}

Answer 6

If you're using jQuery, you can use the jquery.cookie plugin .

Getting the value for a particular cookie is done as follows:

$.cookie('MyCookie'); // Returns the cookie value

Answer 7

regexObject. test ( String ) is faster than string. match ( RegExp ).

The MDN site describes the format for document.cookie, and has an example regex to grab a cookie ( document.cookie.replace(/(?:(?:^|.*;\\s*)test2\\s*\\=\\s*([^;]*).*$)|^.*$/, "$1"); ). Based on that, I'd go for this:

/^(.*;)?\s*cookie1\s*=/.test(document.cookie);

The question seems to ask for a solution which returns false when the cookie is set, but empty. In that case:

/^(.*;)?\s*cookie1\s*=\s*[^;]/.test(document.cookie);

Tests

function cookieExists(input) {return /^(.*;)?\s*cookie1\s*=/.test(input);}
function cookieExistsAndNotBlank(input) {return /^(.*;)?\s*cookie1\s*=\s*[^;]/.test(input);}
var testCases = ['cookie1=;cookie1=345534;', 'cookie1=345534;cookie1=;', 'cookie1=345534;', ' cookie1 = 345534; ', 'cookie1=;', 'cookie123=345534;', 'cookie=345534;', ''];
console.table(testCases.map(function(s){return {'Test String': s, 'cookieExists': cookieExists(s), 'cookieExistsAndNotBlank': cookieExistsAndNotBlank(s)}}));

Answer 8

There are several good answers here. I however prefer [1] not using a regular expression, and [2] using logic that is simple to read, and [3] to have a short function that [4] does not return true if the name is a substring of another cookie name . Lastly [5] we can't use a for each loop since a return doesn't break it.

function cookieExists(name) {
  var cks = document.cookie.split(';');
  for(i = 0; i < cks.length; i++)
    if (cks[i].split('=')[0].trim() == name) return true;
}

Answer 9

function getCookie(name) {

    var dc = document.cookie;
    var prefix = name + "=";
    var begin = dc.indexOf("; " + prefix);
    if (begin == -1) {
        begin = dc.indexOf(prefix);
        if (begin != 0) return null;
        else{
            var oneCookie = dc.indexOf(';', begin);
            if(oneCookie == -1){
                var end = dc.length;
            }else{
                var end = oneCookie;
            }
            return dc.substring(begin, end).replace(prefix,'');
        } 

    }
    else
    {
        begin += 2;
        var end = document.cookie.indexOf(";", begin);
        if (end == -1) {
            end = dc.length;
        }
        var fixed = dc.substring(begin, end).replace(prefix,'');
    }
    // return decodeURI(dc.substring(begin + prefix.length, end));
    return fixed;
} 

Tried @jac function, got some trouble, here's how I edited his function.

Answer 10

instead of the cookie variable you would just use document.cookie.split...

 var cookie = 'cookie1=s; cookie1=; cookie2=test'; var cookies = cookie.split('; '); cookies.forEach(function(c){ if(c.match(/cookie1=.+/)) console.log(true); });

Answer 11

For anyone using Node, I found a nice and simple solution with ES6 imports and the cookie module!

First install the cookie module (and save as a dependency):

npm install --save cookie

Then import and use:

import cookie from 'cookie';
let parsed = cookie.parse(document.cookie);
if('cookie1' in parsed) 
    console.log(parsed.cookie1);

Answer 12

Using Javascript:

 function getCookie(name) {
      let matches = document.cookie.match(new RegExp(
        "(?:^|; )" + name.replace(/([\.$?*|{}\(\)\[\]\\\/\+^])/g, '\\$1') + "=([^;]*)"
      ));
      return matches ? decodeURIComponent(matches[1]) : undefined;
    }

Answer 13

Note that if a cookie is secure, you cannot check in client side for its existence using document.cookie (which all of the answers are using). Such cookie can be checked only at sever side.

Answer 14

Parse cookies with Array.prototype.reduce() into an object (ES6)

const cookies = document.cookie.split(";").reduce((e, t) => {
  const [c, n] = t.trim().split("=").map(decodeURIComponent);
  try { // this can be removed if you do not need JSON cookies parsed
    return Object.assign(e, {
      [c]: JSON.parse(n)
    })
  }
  catch (t) {
    return Object.assign(e, {
      [c]: n
    })
  }
}, {})

Check if your cookie is there

typeof cookies.yourCookie === "string";

Answer 15

If anyone is still looking into this post maybe this will help.

First do a function to get the cookie, something like this..

function getCookie(cname) {
    let name = cname + "=";
    let ca = document.cookie.split(';');
    for(let i = 0; i < ca.length; i++) {
      let c = ca[i];
      while (c.charAt(0) == ' ') {
        c = c.substring(1);
      }
      if (c.indexOf(name) == 0) {
        return c.substring(name.length, c.length);
      }
    }
    return "";
    
  }

Then you could check if the specific cookie exists before doing something else

if( getCookie(mycookieName)){
 // do something....
}

Answer 16

// check if cookie is present 
function is_CookiePresent( cookieName ){

  if( void 0 != cookieName && "" != cookieName && null != cookieName ){

    var is_present = document.cookie.split(";").filter(e=>{
        if(e.trim().split("=").includes(cookieName)) return true;
    })

    if(!is_present.length){return false;}
    return true;

  }
  else{
    return false;
  }

}

// Get cookie name value :) 
function getCookieValue( cookieName ){

  if( void 0 != cookieName && "" != cookieName && null != cookieName ){

    var is_present = document.cookie.split(";").filter(e=>{
        if(e.trim().split("=").includes(cookieName)) return true;
    })

    if(!is_present.length){return false;}
   
    var __CookieValue = is_present.join('').trim();

    return __CookieValue.substring(__CookieValue.indexOf('=')+1);

  }
  else{
    return false;
  }

}

Answer 17

use this method instead:

function getCookie(name) {
    var value = "; " + document.cookie;
    var parts = value.split("; " + name + "=");
    if (parts.length == 2) return parts.pop().split(";").shift();
    else return null;
}

function doSomething() {
    var myCookie = getCookie("MyCookie");

    if (myCookie == null) {
        // do cookie doesn't exist stuff;
    }
    else {
        // do cookie exists stuff
    }
}

Answer 18

/// ************************************************ cookie_exists

/// global entry point, export to global namespace

/// <synopsis>
///   cookie_exists ( name );
///
/// <summary>
///   determines if a cookie with name exists
///
/// <param name="name">
///   string containing the name of the cookie to test for 
//    existence
///
/// <returns>
///   true, if the cookie exists; otherwise, false
///
/// <example>
///   if ( cookie_exists ( name ) );
///     {
///     // do something with the existing cookie
///     }
///   else
///     {
///     // cookies does not exist, do something else 
///     }

function cookie_exists ( name )
  {
  var exists = false;

  if ( document.cookie )
    {
    if ( document.cookie.length > 0 )
      {
                                    // trim name
      if ( ( name = name.replace ( /^\s*/, "" ).length > 0 ) )
        {
        var cookies = document.cookie.split ( ";" );
        var name_with_equal = name + "=";

        for ( var i = 0; ( i < cookies.length ); i++ )
          {
                                    // trim cookie
          var cookie = cookies [ i ].replace ( /^\s*/, "" );

          if ( cookie.indexOf ( name_with_equal ) === 0 )
            {
            exists = true;
            break;
            }
          }
        }
      }
    }

  return ( exists );

  } // cookie_exists

Answer 19

function getcookie(name = '') {
    let cookies = document.cookie;
    let cookiestore = {};
    
    cookies = cookies.split(";");
    
    if (cookies[0] == "" && cookies[0][0] == undefined) {
        return undefined;
    }
    
    cookies.forEach(function(cookie) {
        cookie = cookie.split(/=(.+)/);
        if (cookie[0].substr(0, 1) == ' ') {
            cookie[0] = cookie[0].substr(1);
        }
        cookiestore[cookie[0]] = cookie[1];
    });
    
    return (name !== '' ? cookiestore[name] : cookiestore);
}

To get a object of cookies simply call getCookie()

To check if a cookie exists, do it like this:

if (!getcookie('myCookie')) {
    console.log('myCookie does not exist.');
} else {
    console.log('myCookie value is ' + getcookie('myCookie'));
}

Or just use a ternary operator.

Answer 20

function hasCookie(cookieName){
return document.cookie.split(';')
.map(entry => entry.split('='))
.some(([name, value]) => (name.trim() === cookieName) && !!value);
}

Note: The author wanted the function to return false if the cookie is empty ie cookie=; this is achieved with the && !!value condition. Remove it if you consider an empty cookie is still an existing cookie…

Answer 21

 var cookie = 'cookie1=s; cookie1=; cookie2=test'; var cookies = cookie.split('; '); cookies.forEach(function(c){ if(c.match(/cookie1=.+/)) console.log(true); });

Answer 22

You can verify if a cookie exists and it has a defined value:

function getCookie(cookiename) {
    if (typeof(cookiename) == 'string' && cookiename != '') {
        const COOKIES = document.cookie.split(';');
        for (i = 0; i < COOKIES.length; i++) {
            if (COOKIES[i].trim().startsWith(cookiename)) {
                return COOKIES[i].split('=')[1];
            }
        }
    }

    return null;
}

const COOKIE_EXAMPLE = getCookie('example');
if (COOKIE_EXAMPLE == 'stackoverflow') { ... }
// If is set a cookie named "example" with value "stackoverflow"
if (COOKIE_EXAMPLE != null) { ... }
// If is set a cookie named "example" ignoring the value

It will return null if cookie doesn't exists.