Is there a way to Reflect JavaScript properties and method from a "class" or function, not from an object?

It's very easy to get reflection from a JavaScript object, just as following code.

var getAllMembers = function (obj) {
    var members = {};
    members.properties = [];
    members.methods = [];

    for (var prop in obj) {
        if (typeof obj[prop] != 'function')
            members.properties.push(prop);
        else members.methods.push(prop);
    }
    return members;
}

function demo_class(na, nb) {
    this.a = na;
    this.b = nb;

    this.funca = function () {
        console.log(this.a);
    }
    this.funcb = function () {
        console.log(this.b);
    }
}

var x = new demo_class(1234, 4321);

var members = getAllMembers(x);

console.log(members.properties);  // [ 'a', 'b' ]
console.log(members.methods);     // [ 'funca', 'funcb' ]

My question is: Is there a way to get properties and methods from a class or function, instead of from an object? For example, like this:

var members = getAllMembers(demo_class); // Only can get '[] []'