Operator overloading in Javascript

Question

I'm trying to port this Javascript function (shortened for clarity):

Vertices.scale = function(vertices, scaleX, scaleY, point) {

    point = point || Vertices.centre(vertices);

};

point is a vector, i.e. an object of the form { x: 5, y: 10 }. Vertices.centre(vertices) returns a similar vector object.

As far as I can see, there is no overloading of the '||' operator in the source code. In fact, I don't think you can overload operators in Javascript.

What does this code mean in plain English then?

madox2 · Accepted Answer · 2016-02-21 14:02:44Z

2

It is the same as:

Vertices.scale = function(vertices, scaleX, scaleY, point) {
    if (point) {
        point = point;
    } else {
        point = Vertices.centre(vertices);
    }
}

Convention using || (logical OR operator) is shorthand for using default values for function paramters. (but notice that it won't work for boolean parameters).

You can find more about logical operators on MDN

edited Feb 21, 2016 at 14:02

answered Feb 21, 2016 at 13:49

madox2

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2 Comments

madox2 Over a year ago

It seems so. In javascript you can call function with any number of parameters.

Garry Pettet Over a year ago

Thank you madox2. Very different than the language I'm trying to port this framework too :)

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