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| 1 | +let firstOperand = ""; |
| 2 | +let secondOperand = ""; |
| 3 | +let currentOperator = null; |
| 4 | +let awaitingSecondOperand = false; |
| 5 | + |
| 6 | +const display = document.querySelector(".calculator-screen"); |
| 7 | +const keys = document.querySelector(".calculator-keys"); |
| 8 | + |
| 9 | +const updateDisplay = () => { |
| 10 | + display.value = awaitingSecondOperand ? secondOperand : firstOperand; |
| 11 | +}; |
| 12 | + |
| 13 | +const resetCalculator = () => { |
| 14 | + firstOperand = ""; |
| 15 | + secondOperand = ""; |
| 16 | + currentOperator = null; |
| 17 | + awaitingSecondOperand = false; |
| 18 | + updateDisplay(); |
| 19 | +}; |
| 20 | + |
| 21 | +const inputNumber = (number) => { |
| 22 | + if (awaitingSecondOperand) { |
| 23 | + secondOperand += number; |
| 24 | + } else { |
| 25 | + firstOperand += number; |
| 26 | + } |
| 27 | + updateDisplay(); |
| 28 | +}; |
| 29 | + |
| 30 | +const inputOperator = (operator) => { |
| 31 | + if (!firstOperand) return; |
| 32 | + |
| 33 | + if (secondOperand) { |
| 34 | + calculate(); |
| 35 | + } |
| 36 | + |
| 37 | + currentOperator = operator; |
| 38 | + awaitingSecondOperand = true; |
| 39 | +}; |
| 40 | + |
| 41 | +const inputDecimal = () => { |
| 42 | + if (awaitingSecondOperand) { |
| 43 | + if (!secondOperand.includes(".")) { |
| 44 | + secondOperand += "."; |
| 45 | + } |
| 46 | + } else { |
| 47 | + if (!firstOperand.includes(".")) { |
| 48 | + firstOperand += "."; |
| 49 | + } |
| 50 | + } |
| 51 | + updateDisplay(); |
| 52 | +}; |
| 53 | + |
| 54 | +const calculate = () => { |
| 55 | + let result; |
| 56 | + const first = parseFloat(firstOperand); |
| 57 | + const second = parseFloat(secondOperand); |
| 58 | + |
| 59 | + if (Number.isNaN(first) || Number.isNaN(second)) return; |
| 60 | + |
| 61 | + switch (currentOperator) { |
| 62 | + case "+": |
| 63 | + result = first + second; |
| 64 | + break; |
| 65 | + case "-": |
| 66 | + result = first - second; |
| 67 | + break; |
| 68 | + case "*": |
| 69 | + result = first * second; |
| 70 | + break; |
| 71 | + case "/": |
| 72 | + result = first / second; |
| 73 | + break; |
| 74 | + default: |
| 75 | + return; |
| 76 | + } |
| 77 | + |
| 78 | + firstOperand = String(result); |
| 79 | + secondOperand = ""; |
| 80 | + awaitingSecondOperand = false; |
| 81 | + currentOperator = null; |
| 82 | + updateDisplay(); |
| 83 | +}; |
| 84 | + |
| 85 | +keys.addEventListener("click", (event) => { |
| 86 | + const { target } = event; |
| 87 | + const { value } = target; |
| 88 | + |
| 89 | + if (!target.matches("button")) return; |
| 90 | + |
| 91 | + switch (value) { |
| 92 | + case "all-clear": |
| 93 | + resetCalculator(); |
| 94 | + break; |
| 95 | + case "=": |
| 96 | + calculate(); |
| 97 | + break; |
| 98 | + case ".": |
| 99 | + inputDecimal(); |
| 100 | + break; |
| 101 | + case "+": |
| 102 | + case "-": |
| 103 | + case "*": |
| 104 | + case "/": |
| 105 | + inputOperator(value); |
| 106 | + break; |
| 107 | + default: |
| 108 | + if (Number.isInteger(parseFloat(value))) { |
| 109 | + inputNumber(value); |
| 110 | + } |
| 111 | + } |
| 112 | +}); |
| 113 | + |
| 114 | +document.addEventListener("DOMContentLoaded", updateDisplay); |
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