Function Run Once

[Aidanx]

I am using an alert function to warn visitors to my site of expletive content and I want to set the javascript to run this alert only once. Tips?

[Bob90]

Use cookies or PHP 'sessions'.



There are many examples either in this forum or on the web.

[Aidanx]

How do I set one up?

[Twey]

You can also do it with Javascript:

if(typeof Twey === "undefined")
  Twey = {
    'GLOBAL' : this
  };

Twey.Pythonic = {
  'Array' : {
    'filter' : function(f) {
      for(var i = 0, r = []; i < this.length; ++i)
        if((typeof f === "function" && f(this[i])) || (typeof f === "string" && this[i][f]))
          r.push(this[i]);
      return r;
    },

    'map' : function(f) {
      for(var i = 0, r = []; i < this.length; ++i)
        r.push(f(this[i]));
      return r;
    },

    'reduce' : function(f) {
      if(this.length === 0)
        return null;
      for(var i = 1, c = this[0]; i < this.length; ++i)
        c = f(c, this[i]);
      return c;
    },
  },

  'LOAD' : function(n) {
    var n = n.split("."),
      o = n[0],
      f = n[1];
    return !!(
      Twey.GLOBAL[o] &&
      Twey.GLOBAL[o].prototype &&
      typeof Twey.GLOBAL[o].prototype[f] === "undefined" &&
      this[o] &&
      this[o][f] &&
      (Twey.GLOBAL[o].prototype[f] = this[o][f])
    );
  }
};

Twey.Pythonic.LOAD("Array.filter");
Twey.Pythonic.LOAD("Array.map");
Twey.Pythonic.LOAD("Array.reduce");

function Hash(kvals) {
  for(var i = 0; i < kvals.length; ++i)
    this[kvals[0]] = kvals[1];
}

Hash.prototype.toArray = function() {
  var r = [];
  for(var x in this)
    if(this.hasOwnProperty(x))
      r.push([x, this[x]]);
  return r;
};

function cookieToHash(cookie) {
  return new Hash(cookie.split(";").map(function(a) { return a.split("=").map(decodeURIComponent); }));
};

function hashToCookie(hash) {
  return hash.toArray().map(function(a) { return a.map(encodeURIComponent).join("="); }).join(";");
};

onload = function() {
  var hashBrown = cookieToHash(document.cookie);
  if(!hashBrown['warned'])
    if(!confirm("This site contains adult material.  Are you sure you want to proceed?"))
      location.replace("http://www.google.com/");
    else {
      hashBrown['warned'] = "yes";
      document.cookie = hashToCookie(hashBrown);
    }
}

Note that users without Javascript won't be warned, though.

[Bob90]

//http://www.quirksmode.org/js/cookies.html
function createCookie(name,value,days) {
	if (days) {
		var date = new Date();
		date.setTime(date.getTime()+(days*24*60*60*1000));
		var expires = "; expires="+date.toGMTString();
	}
	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);
}

Just use these functions. Create a function that is called onload and checks the content of a cookie. like this.

if(readCookie('warning') !== 'warned')
{alert('There is some durty stuff on this site!')
createCookie('warning','warned',7) 
}

[alexjewell]

Twey, your scripts crack me up. Haha.

hashBrown? That's great.

[Twey]

Just use these functions.

I preferred mine. It's more verbose, but also neater, and the functions are quite reusable. It's a matter of taste, though.

Twey, your scripts crack me up. Haha.

hashBrown? That's great.

All that talk of cookies and hashes made me hungry.

[mwinter]

I preferred mine.

As far as I can see, it's defective (in a general sense) in that hashToCookie will collect all of the data, which is later simply assigned: session data must be set one datum at a time. The code also fails to set a lifetime, which seems to me to be a requirement for the OP.


If we're going to bandy implementations about, I'll include mine, below. Thus far, it's the only one to provide code to check for cookie support - people do disable them, you know!

var Session = function () {
    var supported = false;

    return {
        get : function (name) {
            var match = new RegExp('(^|;)\\s*' + name
                    + '\\s*=\\s*([^\\s;]+)').exec(document.cookie);

            return match ? match[2] : null;
        },
        set : function (name, value, maxAge, path, domain) {
            var cookie = name + '=' + value;

            if (typeof maxAge == 'number') {
                var expires = new Date();

                expires.setUTCSeconds(maxAge + expires.getUTCSeconds());
                cookie += ';expires=' + expires.toGMTString();
            }
            if (typeof path == 'string') cookie += ';path=' + path;
            if (typeof domain == 'string') cookie += ';domain=' + domain;
            document.cookie = cookie;
        },
        remove : function (name, path, domain) {
            this.set(name, 'deleted', -1, path, domain);
        },
        isSupported : function () {
            if (typeof document.cookie == 'string') {
                var name = 'test', value = 'fubar';

                while (this.get(name) != null) name += name;
                this.set(name, value);
                if ((this.get(name) == value) && (this.get('expires') == null)) {
                    this.remove(name);
                    supported = (this.get(name) == null);
                }
            }
            return (this.isSupported = function () {return supported;})();
        },
        makeAge : function (days, hours, minutes, seconds) {
            return ((days * 24 + (+hours || 0)) * 60 + (+minutes || 0)) * 60 + (+seconds || 0);
        }
    };
}();

Date.prototype.toGMTString = function () {
    var days = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'],
        months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov',
            'Dec'];

    return function () {
        return days[this.getUTCDay()] + ', ' + this.getUTCDate().pad(2) + '-'
            + months[this.getUTCMonth()] + '-' + this.getUTCFullYear().pad(4) + ' '
            + this.getUTCHours().pad(2) + ':' + this.getUTCMinutes().pad(2) + ':'
            + this.getUTCSeconds().pad(2) + ' GMT';
    };
}();

Number.prototype.pad = function (length, radix, character) {
    return (+this).toString(+radix || 10).pad(length, character || '0');
};

String.prototype.pad = function (length, character) {
    var result = String(this);
    character = character || ' ';

    while (result.length < length) result = character + result;
    return result;
};

[Twey]

As far as I can see, it's defective (in a general sense) in that hashToCookie will collect all of the data, which is later simply assigned: session data must be set one datum at a time.

Could you elucidate on this a little? You're saying that it's wrong to simply assign a whole string and overwrite document.cookie?

[mwinter]

You're saying that it's wrong to simply assign a whole string and overwrite document.cookie?

Yes. When reading, all session data is included separated by semicolons. However, if you have lots of session data to set, each name/value pair must be assigned individually. In the latter case, semicolons separate parameters, such as expiry date and applicable path, from the session data.