stop form submission

<form method="post" name="frm1" action="add.php">

<input  type="text"   value="aaaaa" >

<input  type="text"   value="aaaaa" >

<input type="button" value="cagir" onclick="call();">

</form>

<script>

function call(){

      if(condition){

         document.forms['frm1'].submit();   // action form  add.php

       }else{

        alert("stop action");

    }

}

</script>