In this exercise we will build a simple counter API using express.

• Explain how to set up and run an Express application
• Build a simple Express API and send a HTTP request to an available endpoint using a HTTP client
• Explain that JSON is a widely-used language-agnostic format for encoding data as attribute value pairs
• Diagram the request and response cycle for an Express API.
• Use console.log() and read the result in the server logs

Create a new express application using the steps provided in the express intro.

Ypur application should maintain a simple numeric counter and provide the following endpoints that allow a client to retrieve and manipulate the counter:

• GET /counter - Returns the current value of the counter. The counter should start of at 0.
• POST /counter/increment- Increments the counter on the server and returns the current value.
• POST /counter/decrement- Decrements a counter on the server and returns the current value.
• POST /counter/double- Double the value of the counter on the server and returns the current value.
• DELETE /counter - Resets the counter to 0 and returns the current value.

All endpoints should return the current value of the counter in following format: { counter: 0 }

Test each route using:

• fetch
• curl
• An API testing tool such as postman or insomnia

Add a route PUT /counter that can be used to set the counter to a specific value. The value should be specified by a query string parameter. For example, making a PUT request to /counter?value=20 should set the value of the counter to 20. Use the req.query property in your callback to get the value provided. See the express documentation If no value is provided, the counter should not be changed.

Using route parameters, update your API to keep track of multiple counters. Allow the client to specify the counter name as part of the URL. For example, to update and access a counter called "cars", the client could make the following requests:

• POST /counter/cars/increment
• POST /counter/cars/decrement
• POST /counter/cars/double
• DELETE /counter/cars
• GET /counter/cars

It should be possible for the client to specify any counter name in the place of "cars".