Why do my custom javascript modules not work anymore after updating bootstrap?
locate the javascript file where you have your error throwing code:

$(document).ready(function(){var weatherAPI='http://api.openweathermap.org/data/2.5/weather';var data={q:"Athens",units:"metric",appid:"b0847a3de80121926a9f428c35f611f8"};function showWeather(weatherReport){var iconURL='http://openweathermap.org/img/w/'+ weatherReport.weather[0].icon+'.png';var imgE=document.createElement('img');$("#open-weather").attr('src',iconURL);$('#temperature').html('&amp;#913;&amp;#952;&amp;#942;&amp;#957;&amp;#945; '+ weatherReport.main.temp+'&amp;#176;');}
$.getJSON(weatherAPI,data,showWeather);});;function dateAndTime(){var date=new Date();var day;var dayOfMonth=date.getDate();var month;var h=date.getHours();var m=date.getMinutes();var s=date.getSeconds();switch(date.getDay()){case 0:day="&amp;#922;&amp;#965;&amp;#961;&amp;#953;&amp;#945;&amp;#954;&amp;#942;";break;case 1:day="&amp;#916;&amp;#949;&amp;#965;&amp;#964;&amp;#941;&amp;#961;&amp;#945;";break;case 2:day="&amp;#932;&amp;#961;&amp;#943;&amp;#964;&amp;#951;";break;case 3:day="&amp;#932;&amp;#949;&amp;#964;&amp;#940;&amp;#961;&amp;#964;&amp;#951;";break;case 4:day="&amp;#928;&amp;#941;&amp;#956;&amp;#960;&amp;#964;&amp;#951;";break;case 5:day="&amp;#928;&amp;#945;&amp;#961;&amp;#945;&amp;#963;&amp;#949;&amp;#954;&amp;#965;&amp;#942;";break;case 6:day="&amp;#931;&amp;#940;&amp;#946;&amp;#946;&amp;#945;&amp;#964;&amp;#959;";break;}
switch(date.getMonth()){case 0:month="&amp;#921;&amp;#945;&amp;#957;&amp;#959;&amp;#965;&amp;#945;&amp;#961;&amp;#943;&amp;#959;&amp;#965;";break;case 1:month="&amp;#934;&amp;#949;&amp;#946;&amp;#961;&amp;#959;&amp;#965;&amp;#945;&amp;#961;&amp;#943;&amp;#959;&amp;#965;";break;case 2:month="&amp;#924;&amp;#945;&amp;#961;&amp;#964;&amp;#943;&amp;#959;&amp;#965;";break;case 3:month="&amp;#913;&amp;#960;&amp;#961;&amp;#953;&amp;#955;&amp;#943;&amp;#959;&amp;#965;";break;case 4:month="&amp;#924;&amp;#945;&amp;#970;&amp;#959;&amp;#965;";break;case 5:month="&amp;#921;&amp;#959;&amp;#965;&amp;#957;&amp;#943;&amp;#959;&amp;#965;";break;case 6:month="&amp;#921;&amp;#959;&amp;#965;&amp;#955;&amp;#943;&amp;#959;&amp;#965;";break;case 7:month="&amp;#913;&amp;#965;&amp;#947;&amp;#959;&amp;#973;&amp;#963;&amp;#964;&amp;#959;&amp;#965;";break;case 8:month="&amp;#931;&amp;#949;&amp;#960;&amp;#964;&amp;#949;&amp;#956;&amp;#946;&amp;#961;&amp;#943;&amp;#959;&amp;#965;";break;case 9:month="&amp;#927;&amp;#954;&amp;#964;&amp;#969;&amp;#946;&amp;#961;&amp;#943;&amp;#959;&amp;#965;";break;case 10:month="&amp;#925;&amp;#959;&amp;#949;&amp;#956;&amp;#946;&amp;#961;&amp;#943;&amp;#959;&amp;#965;";break;case 11:month="&amp;#916;&amp;#949;&amp;#954;&amp;#949;&amp;#956;&amp;#946;&amp;#961;&amp;#943;&amp;#959;&amp;#965;";break;}
if(h&lt;10){h="0"+ h;}
if(m&lt;10){m="0"+ m;}
if(s&lt;10){s="0"+ s;}
var time=h+":"+ m+":"+ s;$('#time-now').html(time);setTimeout('dateAndTime();','1000');var myDate=day+', '+ dayOfMonth+" "+ month;$('#date-now').html(myDate);return true;};


then wrap it with

(function($) {
..
})(jQuery);


or replace the $ sign with jQuery