JavaScript Calculator Project

In this tutorial, we will learn how to create a simple Calculator project in JavaScript.

We are going to use vanilla JavaScript to develop this Calculator project.

JavaScript Calculator Project

Create a folder called calculator as project workspace, and we will create all the project files inside this folder.

1. index.html

Let's create index.html and add the following code to it:

<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>Calculator</title> <link href="style.css" rel="stylesheet"> <script src="script.js" defer></script> </head> <body> <div class="calculator-grid"> <div class="output"> <div data-previous-operand class="previous-operand"></div> <div data-current-operand class="current-operand"></div> </div> <button data-all-clear class="span-two">AC</button> <button data-delete>DEL</button> <button data-operation>รท</button> <button data-number>1</button> <button data-number>2</button> <button data-number>3</button> <button data-operation>*</button> <button data-number>4</button> <button data-number>5</button> <button data-number>6</button> <button data-operation>+</button> <button data-number>7</button> <button data-number>8</button> <button data-number>9</button> <button data-operation>-</button> <button data-number>.</button> <button data-number>0</button> <button data-equals class="span-two">=</button> </div> </body> </html>

2. script.js

Let's create a JavaScript file named script.js and add the following JavaScript code to it:

class Calculator { constructor(previousOperandTextElement, currentOperandTextElement) { this.previousOperandTextElement = previousOperandTextElement this.currentOperandTextElement = currentOperandTextElement this.clear() } clear() { this.currentOperand = '' this.previousOperand = '' this.operation = undefined } delete() { this.currentOperand = this.currentOperand.toString().slice(0, -1) } appendNumber(number) { if (number === '.' && this.currentOperand.includes('.')) return this.currentOperand = this.currentOperand.toString() + number.toString() } chooseOperation(operation) { if (this.currentOperand === '') return if (this.previousOperand !== '') { this.compute() } this.operation = operation this.previousOperand = this.currentOperand this.currentOperand = '' } compute() { let computation const prev = parseFloat(this.previousOperand) const current = parseFloat(this.currentOperand) if (isNaN(prev) || isNaN(current)) return switch (this.operation) { case '+': computation = prev + current break case '-': computation = prev - current break case '*': computation = prev * current break case 'รท': computation = prev / current break default: return } this.currentOperand = computation this.operation = undefined this.previousOperand = '' } getDisplayNumber(number) { const stringNumber = number.toString() const integerDigits = parseFloat(stringNumber.split('.')[0]) const decimalDigits = stringNumber.split('.')[1] let integerDisplay if (isNaN(integerDigits)) { integerDisplay = '' } else { integerDisplay = integerDigits.toLocaleString('en', { maximumFractionDigits: 0 }) } if (decimalDigits != null) { return `${integerDisplay}.${decimalDigits}` } else { return integerDisplay } } updateDisplay() { this.currentOperandTextElement.innerText = this.getDisplayNumber(this.currentOperand) if (this.operation != null) { this.previousOperandTextElement.innerText = `${this.getDisplayNumber(this.previousOperand)} ${this.operation}` } else { this.previousOperandTextElement.innerText = '' } } } const numberButtons = document.querySelectorAll('[data-number]') const operationButtons = document.querySelectorAll('[data-operation]') const equalsButton = document.querySelector('[data-equals]') const deleteButton = document.querySelector('[data-delete]') const allClearButton = document.querySelector('[data-all-clear]') const previousOperandTextElement = document.querySelector('[data-previous-operand]') const currentOperandTextElement = document.querySelector('[data-current-operand]') const calculator = new Calculator(previousOperandTextElement, currentOperandTextElement) numberButtons.forEach(button => { button.addEventListener('click', () => { calculator.appendNumber(button.innerText) calculator.updateDisplay() }) }) operationButtons.forEach(button => { button.addEventListener('click', () => { calculator.chooseOperation(button.innerText) calculator.updateDisplay() }) }) equalsButton.addEventListener('click', button => { calculator.compute() calculator.updateDisplay() }) allClearButton.addEventListener('click', button => { calculator.clear() calculator.updateDisplay() }) deleteButton.addEventListener('click', button => { calculator.delete() calculator.updateDisplay() })

3. style.css

Let's create a CSS file named style.css and add the following CSS code to it:

*, *::before, *::after { box-sizing: border-box; font-family: Gotham Rounded, sans-serif; font-weight: normal; } body { padding: 0; margin: 0; background: linear-gradient(to right, #00AAFF, #00FF6C); } .calculator-grid { display: grid; justify-content: center; align-content: center; min-height: 100vh; grid-template-columns: repeat(4, 100px); grid-template-rows: minmax(120px, auto) repeat(5, 100px); } .calculator-grid > button { cursor: pointer; font-size: 2rem; border: 1px solid white; outline: none; background-color: rgba(255, 255, 255, .75); } .calculator-grid > button:hover { background-color: rgba(255, 255, 255, .9); } .span-two { grid-column: span 2; } .output { grid-column: 1 / -1; background-color: rgba(0, 0, 0, .75); display: flex; align-items: flex-end; justify-content: space-around; flex-direction: column; padding: 10px; word-wrap: break-word; word-break: break-all; } .output .previous-operand { color: rgba(255, 255, 255, .75); font-size: 1.5rem; } .output .current-operand { color: white; font-size: 2.5rem; }

Open index.html in Browser

Let's open the index.html file in the browser, and you will be able to see the following screen:

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