[JS] JS Calculator Program Error

[gulshan212]

Hello this is Gulshan Negi
I am writing a JavaScript program for making a calculator but it shows some error at the time of execution.
Source Code:

const calculator = {
displayValue: '0',
firstOperand: null,
waitingForSecondOperand: false,
operator: null,
};

function inputDigit(digit) {
const { displayValue, waitingForSecondOperand } = calculator;

if (waitingForSecondOperand === true) {
calculator.displayValue = digit;
calculator.waitingForSecondOperand = false;
} else {
calculator.displayValue = displayValue === '0' ? digit : displayValue + digit;
}
}

function inputDecimal(dot) {
if (calculator.waitingForSecondOperand === true) {
calculator.displayValue = "0."
calculator.waitingForSecondOperand = false;
return
}

if (!calculator.displayValue.includes(dot)) {
calculator.displayValue += dot;
}
}

function handleOperator(nextOperator) {
const { firstOperand, displayValue, operator } = calculator
const inputValue = parseFloat(displayValue);

if (operator && calculator.waitingForSecondOperand) {
calculator.operator = nextOperator;
return;
}


if (firstOperand == null && !isNaN(inputValue)) {
calculator.firstOperand = inputValue;
} else if (operator) {
const result = calculate(firstOperand, inputValue, operator);

calculator.displayValue = `${parseFloat(result.toFixed(7))}`;
calculator.firstOperand = result;
}

calculator.waitingForSecondOperand = true;
calculator.operator = nextOperator;
}

function calculate(firstOperand, secondOperand, operator) {
if (operator === '+') {
return firstOperand + secondOperand;
} else if (operator === '-') {
return firstOperand - secondOperand;
} else if (operator === '*') {
return firstOperand * secondOperand;
} else if (operator === '/') {
return firstOperand '/' secondOperand;
}

return secondOperand;
}

function resetCalculator() {
calculator.displayValue = '0';
calculator.firstOperand = null;
calculator.waitingForSecondOperand = false;
calculator.operator = null;
}

function updateDisplay() {
const display = document.querySelector('.calculator-screen');
display.value = calculator.displayValue;
}

updateDisplay();

const keys = document.querySelector('.calculator-keys');
keys.addEventListener('click', event => {
const { target } = event;
const { value } = target;
if (!target.matches('button')) {
return;
}

switch (value) {
case '+':
case '-':
case '*':
case '/':
case '=':
handleOperator(value);
break;
case '.':
inputDecimal(value);
break;
case 'all-clear':
resetCalculator();
break;
default:
if (Number.isInteger(parseFloat(value))) {
inputDigit(value);
}
}

updateDisplay();
});

I also checked and take code reference from , but I don't know what I am doing wrong here. Can anyone give their suggestions on this.
Thanks

[kissein]

function calculate(firstOperand, secondOperand, operator) {
    if (operator === '+') {
        return firstOperand + secondOperand;
    } else if (operator === '-') {
        return firstOperand - secondOperand;
    } else if (operator === '*') {
        return firstOperand * secondOperand;
    } else if (operator === '/') {
        return firstOperand '/' secondOperand; <-- this needs to be / without quotationmarks
    }

    return secondOperand;
}

[gulshan212]

Thanks a lot for your kind response, I will try it.
Thanks again.