gistfile1.js

function count(obj){
    var i=0;
    for(var prop in obj){i++;}
    return i;
}

var a = { a: 1, b: 2 };
console.log(count(a));
var b = function(){};
console.log(count(b));
var c = [1, 2, 3];
console.log(count(c));
var d = [];
d[100] = 1;
console.log(count(d));