addallgametowishlist.js

(function()
{
var wishlist = [];
var wishlisted = [];
 
jQuery.ajax({
type: 'GET',
url: '//api.steampowered.com/ISteamApps/GetAppList/v2',
dataType: 'jsonp',
success: function(result){
jQuery.each(result['applist']['apps'], function(key, value){
wishlist.push(value['appid']);
})
 
jQuery.ajax({
type: 'GET',
url: 'https://store.steampowered.com/dynamicstore/userdata/',
dataType: 'json',
success: function(result) {
jQuery.each(result['rgWishlist'], function (index, value) {
wishlisted.push(value);
});
 
var Index;
for (var i=0; i<wishlisted.length; i++) {
Index = wishlist.indexOf(wishlisted);
                        if (Index > -1) {
                            wishlist.splice(Index, 1);
                        }
                    }
                   
                    var i = 0,
                    loaded = 0,
                    total = wishlist.length,
                    modal = ShowBlockingWaitDialog( 'Executing...',
                        'Please wait until all requests finish. Ignore all the errors, let it finish.' );
 
                    var ExecuteRequest = function( )
                    {
                        jQuery.ajax(
                        {
                            type: 'POST',
                            dataType: 'text',
                            url: '//store.steampowered.com/api/addtowishlist',
                            data:
                            {
                                appid: wishlist[ i ],
                                sessionid: g_sessionID,
                            }
                        }
                        ).always( function( )
                            {
                                loaded++;
                               
                                modal.Dismiss();
                               
                                if( loaded >= total )
                                {
                                    ShowAlertDialog( 'All done!', 'Enjoy.' );
                                }
                                else
                                {
                                    modal = ShowBlockingWaitDialog( 'Executing...',
                                        'Loaded ' + loaded + '/' + total + '. Ignore all the errors, let it finish.' );
                                   
                                    i++;
                                   
                                    ExecuteRequest();
                                }
                            }
                        );
                    };
 
                    setTimeout( ExecuteRequest, 1500 );
                },
                error : function(httpReq,status,exception){
                    ShowAlertDialog( status, 'Uh Oh!' );
                }
            })
        },
        error : function(httpReq,status,exception){
            ShowAlertDialog( status, 'Uh Oh!' );
        },
        jsonp: 'jsonp'
    })
}());

Run it on Steam.com web page, at browser console tab.

Hey i also made a Version which dont need Content Security Policy.
Check it out here: https://gist.github.com/justxanderscode/d66d476575e4c67823c69b4091cb96fe

Also the other Updated Version from Awxk is here: https://gist.github.com/justxanderscode/32f6c74af1d4ae62a864612333c42821

sorry for the inconvenience