Edit in JSFiddle

<button id="btnOK">button ok (1st)</button><br/>
<button id="btnOK">button ok (2nd)</button><br/>
<button id="btnOK">button ok (3rd)</button><br/>
<button id="btnOK">button ok (4th)</button><br/>
<hr/><br/>
<button id="btnReload">Reload</button><br/><br/>
<button id="btnHideWithID">Hide buttons with ID selector</button><br/><br/>
<button id="btnHideWithAttr">Hide buttons with attribute selector</button>

$("#btnHideWithID").on("click",function(){
   $("#btnOK").hide(); 
});

$("#btnHideWithAttr").on("click",function(){
   $("[id='btnOK']").hide(); 
});

$("#btnReload").on("click",function(){
   $("[id='btnOK']").show(); 
});