Line class

function Line(placePoint, endPoint) {
    this.placePoint = placePoint;
    this.endPoint   = endPoint;

    this.testWith   = function(lineB) {
        var lambdaA = this.getLambda(lineB);

        if(lambdaA >= 0 && lambdaA <= 1) {
            var lambdaB = lineB.getLambda(this);
            if(lambdaB >= 0 && lambdaB <= 1) {
                // return the point of intersection:
                return lineB.getDirectionPoint().multiply(lambdaA).add(placePoint);
            }
        }

        return null;
    }

    this.getLambda = function(lineB) {
        var rn = this.getDirectionPoint().dotProduct(lineB.getNormalized());
        var sn = placePoint.dotProduct(lineB.getNormalized());

        return (lineB.getConstante() - sn) / rn;
    }

    this.getDirectionPoint = function() {
        // Vector AB = B-A
        return endPoint.substract(placePoint);
    }

    this.getNormalized = function(lineB) {
        return this.getDirectionPoint().perp().normalize();
    }

    this.getConstante = function() {
        return placePoint.dotProduct(this.getNormalized());
    }
}