javascript - how to stop firing an event using java script -

i have "onclick" event , "onclientclick" event. "onclientclickevent" javascript function , "onclick event" runs on server. want way prevent firing on click event javascript function.scenario that-

asp:button id="button1" runat="server" text="submit" onclick="button1_click" onclientclick="javascript:anscheck()" /> 

you can this:

<asp:button id="button1" runat="server" text="submit" onclick="button1_click" onclientclick="javascript:return anscheck()" /> 

javascript

 funcion anscheck(){     //based on code , condition can return     if(condition){         return true // fire server side event     }     else{         return false; // not fire server event     }   } 

or

<asp:button id="button1" runat="server" text="submit" onclick="button1_click" onclientclick="javascript:return anscheck() return false;" />