JavaScript: Building simple instantiable objects.

Simple function to instantiate Circles. Note the ability to accept random parameter properties, overwrite default properties, and limit the set of permissible parameter properties.

var Circle = function(properties) {
    var newCircle = {
        radius: 2,
        getRadius: function() {
            return this.radius;
        }
    };
    for (o in properties) {
        if (! o.match(/b(radius|hollow)b/i)) {
            console.log("deleting "+o);
            var x = delete o;
            console.log(x);

        }
    }
    jQuery.extend(newCircle, properties);
    return newCircle;
}

var x1 = new Circle({radius:3});
var x2 = new Circle({radius:5, trojan: 10, hollow: "true"});
var x3 = new Circle();

console.log(x1.getRadius());
console.log(x2.getRadius());
console.log(x3.getRadius());

The code above uses a jQuery function to extend our object with the properties object. This approach would almost always be acceptable to me, but what if a client felt it was necessary to create private variables and force their users to stick with the API? We can use closures to get private instance variables.

var Circle = function(properties) {
    var radius = 2;
    var newCircle = {
        getRadius: function() {
            return radius;
        },
        setRadius: function(num) {
            radius = num;
            return true;
        }
    };
    for (o in properties) {
        if (! o.match(/b(radius|hollow)b/i)) {
            console.log("deleting "+o);
            var x = delete o;
            console.log(x);

        } else if (o.match(/b(radius)b/)) {
            newCircle.setRadius(properties[o]);
        }
    }
    return newCircle;
}

var x1 = new Circle({radius:3});
var x2 = new Circle({radius:5, trojan: 10, hollow: "true"});
var x3 = new Circle();

console.log(x1.getRadius());
console.log(x2.getRadius());
console.log(x3.getRadius());

console.log(x1.radius);