MultiMethodJS

Multiple dispatch for JavaScript

Installation

The file "multi_method.js" is located at directory "public_html/src/". Only this single JavaScript file is required.

Usage

var a, collide_message, g, s, score;

function Asteroid() {
    this.point = 1;
}

function Spaceship() {
    this.point = 10;
}

function GiantSpaceship() {
    // Spaceship.call(this);
    this.point = 100;
}

GiantSpaceship.prototype = create_prototype(Spaceship.prototype);

multi_method('collide', [Asteroid, Spaceship], function (a, b) {
    collide_message = 'Behavior when asteroid hits spaceship';
    return a.point + b.point;
});

multi_method('collide', [Spaceship, Spaceship], function (a, b) {
    collide_message = 'Behavior when spaceship hits spaceship';
    return a.point + b.point;
});

multi_method('collide', [Spaceship, Asteroid], function (a, b) {
    collide_message = 'Behavior when spaceship hits asteroid';
    return a.point + b.point;
});

multi_method('collide', [Asteroid, Asteroid], function (a, b) {
    collide_message = 'Behavior when asteroid hits asteroid';
    return a.point + b.point;
});

multi_method('collide', [GiantSpaceship, GiantSpaceship], function (a, b) {
    collide_message = 'Behavior when giant spaceship hits giant spaceship';
    return a.point + b.point;
});

multi_method('collide', ['string', 'number'], function (a, b) {
    collide_message = 'Behavior when ' + a.toString() + ' hits ' + typeof b;
    return 0;
});

a = new Asteroid();
s = new Spaceship();
g = new GiantSpaceship();
score = 0;
score += collide(a, s); // score = 11, collide_message = 'Behavior when asteroid hits spaceship'
score += collide(s, s); // score = 31, collide_message = 'Behavior when spaceship hits spaceship'
score += collide(s, a); // score = 42, collide_message = 'Behavior when spaceship hits asteroid'
score += collide(a, a); // score = 44, collide_message = 'Behavior when asteroid hits asteroid'
score += collide(g, g); // score = 244, collide_message = 'Behavior when giant spaceship hits giant spaceship'
score += collide(g, a); // score = 345, collide_message = 'Behavior when spaceship hits asteroid'
score += collide('apple', 3.14); // score = 345, collide_message = 'Behavior when apple hits number'

Method Ambiguities

The last method definition which the argument type(s) matching the argument(s) would be used when calling the function. There would be no warning for any ambiguity.