What is the "best" way to get and set a single cookie value using JavaScript

Question

I want to increment a cookie value every time a page is referenced even if the page is loaded from cache. What is the "best" or most concise way to implement this?

Answer 1

Stolen from http://www.quirksmode.org/js/cookies.html#script

function createCookie(name,value,days) {
    if (days) {
        var date = new Date();
        date.setTime(date.getTime()+(days*24*60*60*1000));
        var expires = "; expires="+date.toUTCString();
    }
    else var expires = "";
    document.cookie = name+"="+value+expires+"; path=/";
}

function readCookie(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) {
    createCookie(name,"",-1);
}

using it:

var oldCount = parseInt(readCookie('hitCount'), 10) || 0;
createCookie('hitCount', oldCount + 1, 7);

as pointed out in the comments, you should cast to an int since cookies are stored and returned as strings. Using foo++ or ++foo will actually cast for you, but it's safer to know exactly what you're working with:

var x = "5";  // x = "5" (string)
x += 1;       // x = "51" (string!)
x += 5;       // x = "515" (string!)
++x;          // x = 516 (number)