liabru-matter-js/examples/attractorsPlugin.js

(function() {

    var Body = Matter.Body,
        Common = Matter.Common,
        Composite = Matter.Composite;

    var MatterAttractors = {
        name: 'matter-attractors',

        version: '0.1.0',

        for: 'matter-js@^0.10.0',

        install: function(base) {
            base.Body.create = Common.chain(
                Matter.Body.create,
                MatterAttractors.init
            );

            base.Engine.update = Common.chain(
                Matter.Engine.update,
                MatterAttractors.update
            );
        },

        init: function(body) {
            body = this || body;
            body.attractors = body.attractors || [];
        },

        update: function(engine) {
            engine = this || engine;

            var world = engine.world,
                bodies = Composite.allBodies(world);

            for (var i = 0; i < bodies.length; i += 1) {
                var bodyA = bodies[i],
                    attractors = bodyA.attractors;

                if (attractors && attractors.length > 0) {
                    for (var j = i + 1; j < bodies.length; j += 1) {
                        var bodyB = bodies[j];

                        for (var k = 0; k < attractors.length; k += 1) {
                            var attractor = attractors[k],
                                forceVector = attractor;

                            if (Common.isFunction(attractor)) {
                                forceVector = attractor(bodyA, bodyB);
                            }
                            
                            if (forceVector) {
                                Body.applyForce(bodyB, bodyB.position, forceVector);
                            }
                        }
                    }
                }
            }
        }
    };

    Matter.Plugin.register(MatterAttractors);

    window.MatterAttractors = MatterAttractors;

})();