Which way is best for creating an object in JavaScript? Is `var` necessary before an object property?

Question

So far I saw three ways for creating an object in JavaScript. Which way is best for creating an object and why?

I also saw that in all of these examples the keyword

Answer 1

I guess it depends on what you want. For simple objects, I guess you could use the second methods. When your objects grow larger and you're planning on using similar objects, I guess the first method would be better. That way you can also extend it using prototypes.

Example:

function Circle(radius) {
    this.radius = radius;
}
Circle.prototype.getCircumference = function() {
    return Math.PI * 2 * this.radius;
};
Circle.prototype.getArea = function() {
    return Math.PI * this.radius * this.radius;
}

I am not a big fan of the third method, but it's really useful for dynamically editing properties, for example var foo='bar'; var bar = someObject[foo];.