arrayLikeType (rkatic)

HTML

<ul id="log"></ul>

CSS

li.pass { background: #02C500; }
li.fail { background: red; }

JavaScript

var valids = {
    "array": [ 0 ],
    "array like object": { length: 0, 0: 0 }
};
    
for ( msg in valids ) {
   var obj = valids[ msg ];
    
   var keys = $.map( obj, function( v, k ) {
        return k;
   });
   
   console.log( keys.length );
   var pass = keys.length === 1;
   
   $("<li>").text( msg ).addClass( pass ? "pass" : "fail" ).appendTo("#log");
}