Added missing file for sheet 06.

exercises/06_code_quality/nestedCallbacks.js

@@ -0,0 +1,61 @@
+
+'use strict'
+
+const request = require('request')
+
+getInput('enter base currency', (err, base) => {
+	if (err) {
+		console.log(err.message)
+		process.exit()
+	}
+	base = base.trim()
+	checkValidCurrencyCode(base, err => {
+		if (err) {
+			console.log(err.message)
+			process.exit()
+		}
+		getData(`http://api.fixer.io/latest?base=${base}`, (err, data) => {
+			if (err) {
+				console.log(err.message)
+				process.exit()
+			}
+			const obj = JSON.parse(data)
+			printObject(obj)
+			process.exit()
+		})
+	})
+})
+
+function getInput(prompt, callback) {
+	try {
+		process.stdin.resume()
+		process.stdin.setEncoding('utf8')
+		process.stdout.write(`${prompt}: `)
+		process.stdin.on('data', text => callback(null, text))
+	} catch(err) {
+		callback(err)
+	}
+}
+
+function checkValidCurrencyCode(code, callback) {
+	code = code.trim()
+	request('http://api.fixer.io/latest', (err, res, body) => {
+		if (err) callback(new Error('invalid API call'))
+		const rates = JSON.parse(body).rates
+		if (!rates.hasOwnProperty(code)) callback(new Error(`invalid currency code ${code}`))
+		callback(null, true)
+	})
+}
+
+function getData(url, callback) {
+	request(url, (err, res, body) => {
+		if (err) callback(new Error('invalid API call'))
+		callback(null, body)
+	})
+}
+
+function printObject(data) {
+	const indent = 2
+	const str = JSON.stringify(data, null, indent)
+	console.log(str)
+}