How can I display my output data from Arduino into a web browser?

Ok, so I've created an arduino project to monitorize the parking slots into a parking lot. The program prints on serial every time a car enters in the parking lot. (example: Cars = 1,2,... up to 6). Every time a car wants to leave the parking lot ,a sensor is activating,and the number of cars is updated.(Cars = Cars - 1).

I don't have a display to connect to my arduino setup, so i am thinking to display this Cars variable into a web application. Nothing complicated... I want to know how can i capture the data from arduino (maybe in a database file and update it automatically the value when it changes).Next step, to display it on a web app i am thinking to use express framework.