Vector using the classic prototypical object.

vector.dot.js

function Vector(x, y, z) {
    this.x = x;
    this.y = y;
    this.z = z;
}
Vector.prototype.dot = function(w) {
    return this.x * w.x + this.y * w.y + this.z * w.z;
};
// ... more vector functions