javascript - How to load a server variable only after a specific event? -

i need 2 server variables loaded after var change in db.

right now, load when page loaded , therefore keep value had before event (upvotesref.transaction).

 $('.hp').text("<%= post.upvotes - post.downvotes %> hp"); 

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code:

$('.upvotebutton').click(function () {           var $this = $(this);         if ($this.hasclass("on")) {             $this.removeclass("on");             upvotesref.transaction(function (upvotes) {                  if (!upvotes) {                    upvotes = 0;                 }                   upvotes = upvotes - 1;                   return upvotes;              });              userref.remove();             $('.hp').text("<%= post.upvotes - post.downvotes %> hp"); 

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edit:

i ended creating local variables solve problem. thank answers !

var upvoteslocal = <%= post.upvotes %>; var downvoteslocal = <%= post.downvotes %>;  $('.upvotebutton').click(function () {           var $this = $(this);         if ($this.hasclass("on")) {             $this.removeclass("on");             upvotesref.transaction(function (upvotes) {                  if (!upvotes) {                    upvotes = 0;                 }                   upvotes = upvotes - 1;                   return upvotes;              });              upvoteslocal = upvoteslocal -1             userref.remove();             $('.hp').text((upvoteslocal - downvoteslocal) + " hp") 

you should , update variables after transaction right?
means should happen in callback.
assume using firebase transaction method.
callback should second parameter:

$('.upvotebutton').click(function () {           var $this = $(this);         if ($this.hasclass("on")) {             $this.removeclass("on");             upvotesref.transaction(function (upvotes) {                  if (!upvotes) {                    upvotes = 0;                 }                   upvotes = upvotes - 1;                   return upvotes;              }, updatevotes); //<-- here callback function added             userref.remove();  function updatevotes(error, iscommitted, upvotes) {    //here got new upvotes    //but should request downvotes,    //here need ajax request, see e.g. dez's answer or comments }