calculator

// one().plus().two().equals(); // 3
// two().plus().two().equals(); // 4
// one().one().minus().two().equals(); // 9


// one().plus().one()
// two

// minus
// plus
// equals

class Calculator {
    result;
    opOrder = [];
    constructor(order) { this.opOrder = order }
    one() {
        this.opOrder.push(1)
        return new Calculator(this.opOrder)
    }
    two() {
        this.opOrder.push(2)
        return new Calculator(this.opOrder)
    }
    minus() {
        this.opOrder.push('-')
        return new Calculator(this.opOrder)
    }
    plus() {
        this.opOrder.push('+')
        return new Calculator(this.opOrder)
    }
    equals() {
        let num1 = '';
        let num2 = '';
        let expression = [];
        let result;
        for (let i=0; i<this.opOrder.length; ++i) {
            if (!['+', '-'].includes(this.opOrder[i])) {
                if (expression.length === 2) num2 += this.opOrder[i];
                else num1 += this.opOrder[i];
            } else if (expression.length !== 2) {
                expression.push(num1);
                expression.push(this.opOrder[i]);
            }
            if (num2 !== '' && (['+', '-'].includes(this.opOrder[i]) && expression.length === 2) || i === this.opOrder.length-1) {
                expression.push(num2);
                if (expression[1] === '+')
                    result = Number(expression[0])+ Number(expression[2])
                else if (expression[1] === '-') { 
                result = Number(expression[0]) - Number(expression[2])
                }
                expression = [String(result), this.opOrder[i]];
                num1 = String(result);
                num2 = '';
            }

        } 
        console.log(result);
    }
}

let cal = new Calculator([]);
const ans = cal.one().one().minus().two().plus().one().one().equals()