change-with-precision-normalization.js

/**
 * PROBLEM: Change
 * You are writing a change calculating algorithm that will
 * determine the proper change with the smallest possible amount
 * of coins and bills.
 * For the problem, consider you have:
 * - Bills: 100, 50, 20, 10, 5 and 2
 * - Coins: 1, 0.5, 0.25, 0.10, 0.05 and 0.01
 * 
 * Enough talk... Get coding!
 * 
 */

function findMax(amount) {
    const money = [100, 50, 20, 10, 5, 2, 1, 0.5, 0.25, 0.10, 0.05, 0.01]
        .map(p => normalizePrecision(p))
        .sort((a, b) => a > b)
    return money.find(p => p <= amount)
}

function normalizePrecision(n, type = 'UP') {
    return type === 'UP' ? n * 100 : n / 100
}

function calculateChange(n) {
    let change = []
    n = normalizePrecision(n)

    while (n) {
        let amount = findMax(n)
        change.push(amount)
        n = n - amount
    }
    return change.map(p => normalizePrecision(p, 'DOWN'))
}

let changes = [7.84, 123.99, 250, 3.2]

changes.forEach(change => console.log(
    `Your change is: ${change.toFixed(2).padStart(6, ' ')}\t> ${calculateChange(change).reduce((acc, val) => acc + val + '\t', '')}`))