HW04_T02_Class_Invoice_v1.ts

class Invoice {
    invoiceNumber: string
    clientName: string
    amount: number
    status: string

    constructor(invoiceNumber: string, clientName: string, amount: number, status: string) {
        this.invoiceNumber = invoiceNumber
        this.clientName = clientName
        this.amount = amount
        this.status = status
    }

    markAsPaid(): string | void {
        if (this.status === 'Paid') {
            return 'This invoice has already been paid.'
        }
        this.status = 'Paid'
    }

    changeAmount(newAmount: number): void {
        this.amount = newAmount
    }
}

// Verification
const myInvoice = new Invoice('WY-2179', 'Yutani Corp', 500, 'Pending')

console.log(myInvoice)
// 1. Call markAsPaid()
myInvoice.markAsPaid()
console.log('Status after markAsPaid():', myInvoice.status) // 'Paid'
// Calling markAsPaid() again returns the message
console.log(myInvoice.markAsPaid()) // 'This invoice has already been paid.'
// 2. Call changeAmount() with a new value
myInvoice.changeAmount(750)
console.log('Updated amount:', myInvoice.amount) // 750