Javascript Comprehensive isEmpty Function for Objects

isEmpty.js

var hasOwnProperty = Object.prototype.hasOwnProperty;

function isEmpty(obj) {
    if (obj == null) return true;
    if (obj.length > 0)    return false;
    if (obj.length === 0)  return true;
    if (typeof obj !== "object") return true;
    for (var key in obj) {
        if (hasOwnProperty.call(obj, key)) return false;
    }
    return true;
}