Calculator

Svelte code (@3.46.2)

function chooseOperation(op) {
        if (currentOperand == null && previousOperand == null) return;
        
        if (previousOperand == null) {
            operation = op;
            previousOperand = currentOperand;
            currentOperand = null;
            return;
        }

const prev = parseFloat(previousOperand);
        const current = parseFloat(currentOperand);
        let computation = "";
        
        switch (operation) {
            case "+":
                computation = prev + current;
                break;
            case "-":
                computation = prev - current;
                break;
            case "*":
                computation = prev * current;
                break;
            case "÷":
                computation = prev / current;
                break;
        }

previousOperand = computation.toString();
        operation = op;
        currentOperand = null;
    }

function evaluate() {
        if (operation == null || currentOperand == null || previousOperand == null) return;

const prev = parseFloat(previousOperand);
        const current = parseFloat(currentOperand);
        if (isNaN(prev) || isNaN(current)) return;

let computation = "";
        switch (operation) {
            case "+":
                computation = prev + current;
                break;
            case "-":
                computation = prev - current;
                break;
            case "*":
                computation = prev * current;
                break;
            case "÷":
                computation = prev / current;
                break;
        }

currentOperand = computation.toString();
        operation = null;
        previousOperand = null;
        overwrite = true;
    }

function clear() {
        currentOperand = null;
        previousOperand = null;
        operation = null;
        overwrite = false;
    }

$: displayCurrent = currentOperand || '';
    $: displayPrevious = (previousOperand || '') + 
        (operation ? ' ' + operation : '');
</script>

<div class="calculator-grid">
    <div class="output">
        <div class="previous-operand">{displayPrevious}</div>
        <div class="current-operand">{displayCurrent}</div>
    </div>
    <button class="span-two" on:click={clear}>AC</button>
    <button on:click={deleteDigit}>DEL</button>
    <button on:click={() => chooseOperation('÷')}>÷</button>
    <button on:click={() => addDigit('1')}>1</button>
    <button on:click={() => addDigit('2')}>2</button>
    <button on:click={() => addDigit('3')}>3</button>
    <button on:click={() => chooseOperation('*')}>*</button>
    <button on:click={() => addDigit('4')}>4</button>
    <button on:click={() => addDigit('5')}>5</button>
    <button on:click={() => addDigit('6')}>6</button>
    <button on:click={() => chooseOperation('+')}>+</button>
    <button on:click={() => addDigit('7')}>7</button>
    <button on:click={() => addDigit('8')}>8</button>
    <button on:click={() => addDigit('9')}>9</button>
    <button on:click={() => chooseOperation('-')}>-</button>
    <button on:click={() => addDigit('.')}>.</button>
    <button on:click={() => addDigit('0')}>0</button>
    <button class="span-two" on:click={() => evaluate()}>=</button>
</div>

Svelte code (@3.46.2)

Compiled running javascript app

Compiled javascript