Get a response value and increment

dv.js

function evaluate(context){
  // get response body
	var responseBody = context.getCurrentRequest().getLastExchange().responseBody;
	
	// parse JSON
	var jsonDict = JSON.parse(responseBody);
	
	// access the value we need
	var value = jsonDict.id; // e.g. access the "id" field
	
	// parse int and increment
	return parseInt(value) + 1;
};