todo.js

'use strict'

let data = []

module.exports.clear = () => {
	data = []
}

module.exports.add = (item, qty) => {
	if (item === '') throw new Error('item cannot be empty')
	if (qty === '') throw new Error('qty cannot be empty')
	qty = Number(qty)
	if(isNaN(qty)) throw new Error('qty must be a number')
	let flag = false
	for(const index in data) {
		if (data[index].item === item) {
			data[index].qty += qty
			flag = true
		}
	}
	if(flag === false) data.push({item: item, qty: qty})
}

module.exports.getAll = () => {
	for(const key in data) data[key].key = Number(key)
	return data
}

module.exports.delete = key => {
	console.log(`delete key ${key}`)
	if (key === undefined) throw new Error('key cannot be undefined')
	key = Number(key)
	if (isNaN(key)) throw new Error('key must be a number')
	try {
		this.getAll()[key].key // throws error unless the item with the target key exists
		data.splice(key, 1)
	} catch {
		throw new Error('key has to exist')
	}
}

module.exports.countItems = () => data.length