can i be notified of cookie changes in client side javascript

Question

Can I somehow follow changes to cookies (for my domain) in my client side javascript. For example a function that gets called if a cookie gets changed , deleted or added

Answer 1

Slightly improved (shows a console.log for each changed cookie):

var checkCookie = function() {

var lastCookies = document.cookie.split( ';' ).map( function( x ) { return x.trim().split( /(=)/ ); } ).reduce( function( a, b ) { 
        a[ b[ 0 ] ] = a[ b[ 0 ] ] ? a[ b[ 0 ] ] + ', ' + b.slice( 2 ).join( '' ) :  
        b.slice( 2 ).join( '' ); return a; }, {} );


return function() {

    var currentCookies =  document.cookie.split( ';' ).map( function( x ) { return x.trim().split( /(=)/ ); } ).reduce( function( a, b ) { 
        a[ b[ 0 ] ] = a[ b[ 0 ] ] ? a[ b[ 0 ] ] + ', ' + b.slice( 2 ).join( '' ) :  
        b.slice( 2 ).join( '' ); return a; }, {} );


    for(cookie in currentCookies) {
        if  ( currentCookies[cookie] != lastCookies[cookie] ) {
            console.log("--------")
            console.log(cookie+"="+lastCookies[cookie])
            console.log(cookie+"="+currentCookies[cookie])
        }

    }
    lastCookies = currentCookies;

};
}();

window.setInterval(checkCookie, 100);