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Numbers with units

@RiccardoOdone•Suggest a tip•

Keep track of the currency with a generic class to avoid mixing them.

const dollars: number = 2
const euros: number = 3
dollars + euros // ⛔️ Oops!

class Money<Currency extends string> {
  constructor(readonly currency: Currency, readonly amount: number) {}

  sum(other: Money<Currency>) {
    return new Money(this.currency, this.amount + other.amount)
  }
}

const dollars = new Money('USD', 2)
const euros = new Money('EUR', 3)
dollars.sum(euros) // ✅ Does not compile
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