[Kolyaj]

str="ui-button ui-state-default ui-state-hover ui-state-hover ui-corner-all ui-state-hover";
  
myclass='ui-state-hover';
reg= new RegExp('(^|\\s+)' + myclass + '(?=\\s+|$)', 'gi');
str= str.replace(reg,'');
 
alert(str);