jquery - Continuously Check Time -

First of all, how can i check jQuery continuously and id > & Lt; Div & gt; Tags if the current time is between two set bars? I'm making a clock for a school (where the clock is a website that is sent to the cable on the TV in each room), where each period is expressed as such:

  Lt; Div class = "period 1" & gt; Duration 1: 7: 32-8: 14 & lt; / Div & gt; In fact, the code in the view (an ERB file) is:  
     
 % @ Periods.each do | @period | & Gt%; & Lt; Div class = "duration"% = @ period.id%> & Gt; & Lt;% = @ period.string%>: & lt;% = @ period.start_time.strftime ("% I:% M")% & Gt; & Amp; Ndash; & Lt;% = @ period.and_time.startfight ("% I:% M")%> & Lt; / Div & gt; & Lt;% end% & gt;  
 
 My question is how can I constantly check time, and if it is between the  @ period Start_time  and  @period end_time . If so, then  id = "active"  to  and 
 . 
 
 Add. Do I have to set some for javascript to interface with ruby ​​ .get ? 
 
 
 If you have any questions, please ask. 
 
 
 
 
 You can get it by using the  date ()  object of javascript Are there.  Revision due to clarification of the question  
 
 CSS 
 
 . Active {font-weight: bold; } // or whatever style you have  
 
 javascript 
 
  var loop = setInterval (function () {var d = new date ()} var dh = D.getHours (); var CP = 16; / * CP is your preliminary period before 1600, but it is for me to work with an hour each with increment at present time (8 o'clock) . $ / * ('(' Active '); $ (this) .addClass (' active '); // current and $ (if this add) activate .removeClass (' active '); / / otherwise it is cp + + Remove; // Add one hour each loop Let's assume that each period is 1hr}};}, 60000); // 60000 milliseconds = 1 minute update  
 
 
 
 link to check 
 
 Live example - 
 Live example 2 (Modification) - 
 About Date () -