检查 cookie 是否存在于 javascript 中

Question

我的 rails app 上有以下 JavaScript，我只想在 cookie 不存在时运行它。

function getGeoLocation() {
    navigator.geolocation.getCurrentPosition(setGeoCookie);
}

function setGeoCookie(position) {
    var cookie_val = position.coords.latitude + "|" + position.coords.longitude;
    document.cookie = "lat_lng=" + escape(cookie_val);
}

我正在使用它来调用我的 rails 应用程序上的脚本：

 <%- unless @lat_lng %>
        <script>
            getGeoLocation();
        </script>
  <%- end %>

更新

我根据@Njdhv 的回答更新了我的application.js 文件，但弹出窗口仍然出现。这是我所做的：

function getCookieByName(name) {
var parts = document.cookie.split('; '),
    len = parts.length,
    item, i, ret;
for (i = 0; i < len; ++i) {
    item = parts[i].split('=');
    if (item[0] === name) {
        ret = item[1];
        return ret ? unescape(ret) : '';
    }
    }
 return null;
}

if(getCookieByName('lat_lng') != null){
    console.log('lat_lng')
    function getGeoLocation() {
        navigator.geolocation.getCurrentPosition(setGeoCookie);
    }

    function setGeoCookie(position) {
        var cookie_val = position.coords.latitude + "|" + position.coords.longitude;
       document.cookie = "lat_lng=" + escape(cookie_val);
    }
}else{
//you can put your logic here...
}

Answer 1

我发现了问题所在，我必须在我的视图中更改它：

从此：

 <%- unless @lat_lng %>
    <script>
        getGeoLocation();
    </script>
<%- end %>

到这里：

<% if cookies[:lat_lng].nil? %>
    <script>
        getGeoLocation();
    </script>
<% end %>

Answer 2

当您保存了多个 cookie 时，您的搜索 cookie 可能不是 cookie 数组中的第一个 ccokie，您必须同时搜索“lat_lng”和“lat_lng”。

    var lat_lng;

        if (navigator.cookieEnabled) {
          cookieArray = document.cookie.split(";");
          cookieArray.forEach(myFunction);

          console.log(cookieArray)

          function myFunction(item, index) {
            if (item.split("=")[0] == " lat_lng" || item.split("=")[0] == "lat_lng") {
              lat_lng = item.split("=")[1];
              console.log("lat_lng " + lat_lng)
            }
          }
        }

if(lat_lng == null){

  //what you want to happen

}

Answer 3

您可以使用从当前位置访问的document.cookie 读取所有 cookie。

根据您的要求，在您的application 中需要read 和write cookie，这样您就可以为cockie get、set 和clear（删除）创建自己的Singleton 。

单例模式将特定对象的实例数限制为一个。这个单一实例称为单例。

下面我创建了一个Singleton，名字是cookieUtility

var cookieUtility = (function() {
    return {
        /**
         * Creates a cookie with the specified name and value. Additional settings for the cookie may be optionally specified
         * (for example: expiration, access restriction, SSL).
         * @param {String} name The name of the cookie to set.
         * @param {Object} value The value to set for the cookie.
         * @param {Object} [expires] Specify an expiration date the cookie is to persist until. Note that the specified Date
         * object will be converted to Greenwich Mean Time (GMT).
         * @param {String} [path] Setting a path on the cookie restricts access to pages that match that path. Defaults to all
         * pages ('/').
         * @param {String} [domain] Setting a domain restricts access to pages on a given domain (typically used to allow
         * cookie access across subdomains). For example, "sencha.com" will create a cookie that can be accessed from any
         * subdomain of sencha.com, including www.sencha.com, support.sencha.com, etc.
         * @param {Boolean} [secure] Specify true to indicate that the cookie should only be accessible via SSL on a page
         * using the HTTPS protocol. Defaults to false. Note that this will only work if the page calling this code uses the
         * HTTPS protocol, otherwise the cookie will be created with default options.
         */
        set: function(name, value) {
            var argv = arguments,
                argc = arguments.length,
                expires = (argc > 2) ? argv[2] : null,
                path = (argc > 3) ? argv[3] : '/',
                domain = (argc > 4) ? argv[4] : null,
                secure = (argc > 5) ? argv[5] : false;
            document.cookie = name + "=" + escape(value) + ((expires === null) ? "" : ("; expires=" + expires.toUTCString())) + ((path === null) ? "" : ("; path=" + path)) + ((domain === null) ? "" : ("; domain=" + domain)) + ((secure === true) ? "; secure" : "");
        },
        /**
         * Retrieves cookies that are accessible by the current page. If a cookie does not exist, `get()` returns null. The
         * following example retrieves the cookie called "valid" and stores the String value in the variable validStatus.
         *
         *
         * @param {String} name The name of the cookie to get
         * @return {Object} Returns the cookie value for the specified name;
         * null if the cookie name does not exist.
         */
        get: function(name) {
            var parts = document.cookie.split('; '),
                len = parts.length,
                item, i, ret;
            // In modern browsers, a cookie with an empty string will be stored:
            // MyName=
            // In older versions of IE, it will be stored as:
            // MyName
            // So here we iterate over all the parts in an attempt to match the key.
            for (i = 0; i < len; ++i) {
                item = parts[i].split('=');
                if (item[0] === name) {
                    ret = item[1];
                    return ret ? unescape(ret) : '';
                }
            }
            return null;
        },
        /**
         * Removes a cookie with the provided name from the browser
         * if found by setting its expiration date to sometime in the past.
         * @param {String} name The name of the cookie to remove
         * @param {String} [path] The path for the cookie.
         * This must be included if you included a path while setting the cookie.
         */
        clear: function(name, path) {
            if (this.get(name)) {
                path = path || '/';
                document.cookie = name + '=' + '; expires=Thu, 01-Jan-1970 00:00:01 GMT; path=' + path;
            }
        }
    }
})();

怎么用？

1) 用于获取 cookie

cookieUtility.get('name')//need to pass cookie name

2)用于设置cookie

cookieUtility.set('name','value')//need to pass cookie name and value of cookie 

3) 用于删除 cookie

cookieUtility.clear('name') //need to pass cookie name and path(if required)

Answer 4

javascript 的文档很好地解释了这一点。

使用document.cookie，您可以检查 cookie 是否存在。 只需将其与 if 语句结合起来，看起来就像这样：

if (document.cookie == null) {
// do nothing
}
else {
// run it!
}