TypeScript: Format floating euros to string notation

formatMoney.ts

// Solution
type Formatter<T> = (a: T) => (b: T) => string
const numberFormatter: Formatter<number> = decimals => euros => euros.toFixed(decimals).replace(/\./, ',') + ' €'
const toCurrencyString = numberFormatter(2)

// Tests
const suites: [number, string][] = [
    [-1, "-1,00 €"],
    [0, "0,00 €"],
    [1, "1,00 €"],
    [10.01, "10,01 €"],
    [59.00, "59,00 €"],
    [Math.PI, "3,14 €"],
    [NaN, "NaN €"]
]

for (const [euros, want] of suites) {
    const got = toCurrencyString(euros)

    if (got !== want) {
        throw `Got ${got}, but wanted ${want}`
    }
}

console.log('OK')