Witam, mam problem, ponieważ nie wiem jak napisać funkcje ( kalkulator ):
1.która będzie mi wstawiać znak - przed liczbą ( przycisk " +- " ),
2.która będzie usuwać element(pojedynczo) ( przycisk " <- ").
Resztę funkcji do typowych działań napisałem, ewentualnie proszę o naniesienie poprawek do kodu ( tak by działał :) )



<!doctype html>
<html lang="en">
  
<head>
  
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
    <link rel="stylesheet" href="calculator.css">
</head>
  
<body>
    <div class="calculator">
  
        <input type="text" class="calculator-screen" id="content" value="" disabled />
  
        <div class="calculator-odnosniki">
  
            <button type="button" class="czyszczenie" value="wyczysc">C</button>
            <button type="button" class="operator" style="font-size: 80px;" value="<-">&#x20D6;</button>
            <button type="button" class="operator" value="^">x&sup;</button>
            <button type="button" class="operator" value="%">&#x25;</button>
            <button type="button" class="operator" value="(">&#10088;</button>
            <button type="button" class="operator" value=")">&#10089;</button>
            <button type="button" class="operator" value="pierwiastek">&radic;</button>
            <button type="button" class="operator" value="*">&times;</button>
            <button type="button" value="7">7</button>
            <button type="button" value="8">8</button>
            <button type="button" value="9">9</button>
            <button type="button" class="operator" value="/">&divide;</button>
            <button type="button" value="4">4</button>
            <button type="button" value="5">5</button>
            <button type="button" value="6">6</button>
            <button type="button" class="operator" value="-">&minus;</button>
            <button type="button" value="1">1</button>
            <button type="button" value="2">2</button>
            <button type="button" value="3">3</button>
            <button type="button" class="operator" value="+">&plus;</button>
            <button type="button" value="0">0</button>
            <button type="button" class="decimal" value=",">,</button>
            <button type="button" class="operator" value="+-">&#x00B1;</button>
            <button type="button" class="rownasie operator" value="=">=</button>
  
        </div>
    </div>
    <script>
        const calculator = {
            displayValue: '0',
            firstOperand: null,
            SecondOperand: false,
            operator: null,
        };
  
        function inputDigit(digit) {
            const {
                displayValue,
                SecondOperand
            } = calculator;
  
            if (SecondOperand === true) {
                calculator.displayValue = digit;
                calculator.SecondOperand = false;
            } else {
                calculator.displayValue = displayValue === '0' ? digit : displayValue + digit;
            }
        }
  
        function inputDecimal(dot) {
            if (calculator.SecondOperand === true) return;
  
            if (!calculator.displayValue.includes(dot)) {
  
                calculator.displayValue += dot;
            }
        }
  
        function handOperator(nextOperator) {
            const {
                firstOperand,
                displayValue,
                operator
            } = calculator
            const inputValue = parseFloat(displayValue);
  
            if (operator && calculator.SecondOperand) {
                calculator.operator = nextOperator;
                return;
            }
  
            if (firstOperand == null) {
                calculator.firstOperand = inputValue;
            } else if (operator) {
                const currentValue = firstOperand || 0;
                const result = arthmeticValues[operator](currentValue, inputValue);
  
                calculator.displayValue = String(result);
                calculator.firstOperand = result;
            }
  
            calculator.SecondOperand = true;
            calculator.operator = nextOperator;
        }
  
        const arthmeticValues = {
            '/': (firstOperand, secondOperand) => firstOperand / secondOperand,
  
            '*': (firstOperand, secondOperand) => firstOperand * secondOperand,
  
            '+': (firstOperand, secondOperand) => firstOperand + secondOperand,
  
            '-': (firstOperand, secondOperand) => firstOperand - secondOperand,
  
            '^': (firstOperand, secondOperand) => Math.pow(firstOperand, secondOperand),
  
            'pierwiastek': (firstOperand, secondOperand) => Math.sqrt(secondOperand),
  
            '%': (firstOperand, secondOperand) => (parseInt(firstOperand) * 100) / parseInt(secondOperand),
  
            '=': (firstOperand, secondOperand) => secondOperand
        };
  
        function resetCalculator() {
            calculator.displayValue = '0';
            calculator.firstOperand = null;
            calculator.SecondOperand = false;
            calculator.operator = null;
        }
  
        function updateDisplay() {
            const display = document.querySelector('.calculator-screen');
            display.value = calculator.displayValue;
        }
  
        updateDisplay();
  
        const keys = document.querySelector('.calculator-odnosniki');
        keys.addEventListener('click', (event) => {
            const {
                target
            } = event;
            if (!target.matches('button')) {
                return;
            }
  
            if (target.classList.contains('operator')) {
                handOperator(target.value);
                updateDisplay();
                return;
            }
  
            if (target.classList.contains('decimal')) {
                inputDecimal(target.value);
                updateDisplay();
                return;
            }
  
            if (target.classList.contains('czyszczenie')) {
                resetCalculator();
                updateDisplay();
                return;
            }
  
            inputDigit(target.value);
            updateDisplay();
        });
    </script>
</body>
  
</html>





html {
    font-size: 70%;
    box-sizing: border-box;
}
  
*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: inherit;
}
  
.calculator {
    border: 1px solid #ccc;
    border-radius: 10px;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 500px;
}
  
.calculator-screen {
    width: 100%;
    font-size: 5rem;
    height: 80px;
    border: none;
    background-color: #c09ada;
    color: #fff;
    text-align: right;
    padding-right: 20px;
    padding-left: 10px;
}
  
button {
    height: 60px;
    background-color: #a80054;
    border-radius: 3px;
    border: 2px solid #a80054;
    background-color: transparent;
    font-size: 2rem;
    color: #333;
    background-image: linear-gradient(to bottom, transparent, transparent 50%, rgba(0, 0, 0, .04));
    box-shadow: inset 0 0 0 1px rgba(255, 255, 255, .05), inset 0 1px 0 0 rgba(255, 255, 255, .45), inset 0 -1px 0 0 rgba(255, 255, 255, .15), 0 1px 0 0 rgba(255, 255, 255, .15);
    text-shadow: 0 1px rgba(255, 255, 255, .4);
}
  
button:hover {
    background-color: #f169d4;
}
  
.operator {
    color: #000000;
}
  
.czyszczenie {
    background-color: rgb(219, 157, 206);
    border-color: #a80054;
    color: #fff;
}
  
.czyszczenie:hover {
    background-color: #f169d4;
}
  
.rownasie {
    background-color: rgb(219, 157, 206);
    border-color: #a80054;
    color: rgb(0, 0, 0);
}
  
.rownasie:hover {
    background-color: #f169d4;
}
  
.calculator-odnosniki {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-gap: 20px;
    padding: 20px;
    color: #245233;
}