Change var in if else statement

HTML

<div class="big"></div>
<div class="small"></div>

<!--
swapping out var that is set in body
-->
<script>
    // var;
    // var color;
    // var color =;
    // var color = '';
     //var color = 'cat';
    var color = 'big';
     //var color = 'small';
</script>

CSS

.big {height:100px;width:100px;background:#eaeaea;}
.small {height:50px;width:50px;background:#eaeaea;}

JavaScript

// you need to have the condition defined
// you can't run this w/o condition set
// this is bad
//} else if () {
//}

if ( typeof color === 'undefined' || color != 'big' || color != 'small' ) {
    // if var color returns undefined, is not defined or is defined as something other than 'big' or 'small' set background to dark grey
    $('.big,.small').css('background-color', '#333');       
} else if ( color === 'big' ) {
    // but if it is set to big do something
    $('.big').css('background-color', '#fad400');
} else if ( color === 'small' ) {
    // but if it is set to small do something
    $('.small').css('background-color', '#fad400');
}
$('body').append('<div>' + color + '</div>')