Create a cookie if (and only if) it doesn't already exist

问题

I want to:

1. Check to see if a cookie with name of "query" exists
2. If yes, then do nothing
3. If no, create a cookie "query" with a value of 1

Note: I am using jQuery 1.4.2 and the jQuery cookie plugin.

Does anyone have any suggestions as to how I can do this?

回答1:

if($.cookie('query') === null) { 
    $.cookie('query', '1', {expires:7, path:'/'});
}

Alternatively, you could write a wrapper function for this:

jQuery.lazyCookie = function() {
   if(jQuery.cookie(arguments[0]) !== null) return;
   jQuery.cookie.apply(this, arguments);
};

Then you'd only need to write this in your client code:

$.lazyCookie('query', '1', {expires:7, path:'/'});

回答2:

this??

$.cookie('query', '1'); //sets to 1...
$.cookie('query', null); // delete it...
$.cookie('query'); //gets the value....

if ($.cookie('query') == null){ //Check to see if a cookie with name of "query" exists
  $.cookie('query', '1'); //If not create a cookie "query" with a value of 1.
} // If so nothing.

what more do you want??

回答3:

Similar to Jacobs answer but I prefer to test for undefined.

if($.cookie('query') == undefined){
    $.cookie('query', 1, { expires: 1 });
}

来源：https://stackoverflow.com/questions/2824021/create-a-cookie-if-and-only-if-it-doesnt-already-exist