class Calc {
    public lastSum  = -1

    getSum(n1: number, n2: number) {
        this.lastSum = n1 + n2
        return this.lastSum
    }
}

let calc = new Calc()
let result1 = calc.getSum(5, 3)
//sum is 8

console.log("result1 = " + result1)
console.log("calc.lastSum = " + calc.lastSum)