refactor code

function statement(invoice, plays)
{
	let totalAmound = 0;
	let volumeCredits = 0;
	let result = `Statement for ${invoice.customer}\n`;
	
	const format = new Intl.NumberFormat("en-US",
	    {style: "currency",currency: "USD",minimumFractionDigits:2}
	).format;
	
	for(let perf of invoice.performances) {
		const play = plays[perf.playID];
		let thisAmount = 0;
		switch(play.type) {
			case "tragedy":
			    thisAmount = 40000;
				if (perf.audience > 30) {
					thisAmount += 10000 * (perf.audience - 30);
				}
			break;
			case "comedy":
			    thisAmount = 30000;
				if (perf.audience > 20) {
					thisAmount += 10000 + 500 *(perf.audience - 20);
				}
				thisAmount += 300 * perf.audience;
			break;
			default:
			    throw new Error(`unknown type: ${play.type}`);
				
			
		}
		
		//add volume credits
		volumeCredits += Math.max(perf.audience - 30, 0);
		if ("comedy" === play.type) volumeCredits += Math.floor(perf.audience / 5);
		
		//print line for this order
		result += `${play.name}: ${format(thisAmount/100)} (${perf.audience} seats)\n`;
		totalAmound += thisAmount;
	}
	
	result += `Amount owed is ${format(totalAmound/100)}\n`;
	result += `You earned ${volumeCredits} credits\n`;
	return result;
}

const invoice = {
	"customer": "BigCo",
	"performances": [{
		"playID": "hamlet",
		"audience": 55
	},
	{
		"playID": "as-like",
		"audience": 35
	},
	{
		"playID": "othello",
		"audience": 40
	}]
};

const plays = {
	"hamlet" : {"name":"Hamlet","type":"tragedy"},
	"as-like" : {"name":"As You Like It","type":"comedy"},
	"othello" : {"name":"Othello","type":"tragedy"},
};
//console.log(invoice.performances);
const result = statement(invoice, plays);
console.log(result);