jquery if else issue pls fix

i am trying to make a script that will change the shape of a div i dont get why it is not working can somebody please tell me

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
$(document).ready(function(){
    $(".change").click(function(){
        if($('#block').css('border-radius') == '0px')
            $("#block").css("-moz-border-radius", "50px");
            $("#block").css("-webkit-border-radius", "50px");
            $("#block").css("background-color", "blue");
            $("#block").css("border-radius", "50px");
        elseif($('#block').css('border-radius') == '50px')
            $("#block").css("-moz-border-radius", "0px");
            $("#block").css("-webkit-border-radius", "0px");
            $("#block").css("border-radius", "0px");
            $("#block").css("width", "0px");
            $("#block").css("height", "0px");
            $("#block").css("background-color", "transparent");
            $("#block").css("border-top", "50px solid transparent");
            $("#block").css("border-right", "100px solid red");
            $("#block").css("border-bottom", "50px solid transparent");
        else
            $("#block").css("border-radius", "0px");
            $("#block").css("width", "100px");
            $("#block").css("height", "100px");
            $("#block").css("border-top", "0px solid transparent");
            $("#block").css("background-color", "blue");
            $("#block").css("border-right", "0px solid red");
            $("#block").css("border-bottom", "0px solid transparent");
    });
});