Name: Simple Calculator From WebDevSimplified
Rating: 2.7 (9330 reviews)
Author: rafie

Source code simple calculator from WebDevSimplified

Here are the Youtube link https://youtu.be/j59qQ7YWLxw?si=SQWMUCxT5xfAcfjW

Create a folder for the project, example: simple-calculator
Create three file for HTML, CSS, and Javascript.

HTML Source Code

<!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">
  <!-- 1. Add title of the webpage -->
  <title>Calculator</title>
  <!-- 2. Link to CSS File -->
  <link href="style.css" rel="stylesheet">
  <!-- 3. Link to Javascript File -->
  <script src="app.js" defer></script>
</head>
<body>
  <!-- 4. Create div with class "calculator-grid" for display output and result of calculation -->
  <div class="calculator-grid">
    <div class="output">
      <div data-previous-operand class="previous-operand"></div>
      <div data-current-operand class="current-operand"></div>
    </div>
    <!-- 5. Create button for basic calculation -->
    <button data-all-clear class="span-two">AC</button>
    <button data-delete>DEL</button>
    <button data-operation>÷</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>

CSS Source Code

*, *::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;
}

Javascript Source Code

class Calculator {
    constructor(previousOperandTextElement, currentOperandTextElement) {
// Initialize the calculator with the previous and current operand text elements
      this.previousOperandTextElement = previousOperandTextElement
      this.currentOperandTextElement = currentOperandTextElement
      this.clear() // Call the clear method to reset the calculator
    }

    clear() {
      // Clear the current and previous operands and set the operation to undefined
      this.currentOperand = ''
      this.previousOperand = ''
      this.operation = undefined
    }

    delete() {
      // Delete the last character of the current operand
      this.currentOperand = this.currentOperand.toString().slice(0, -1)
    }

    appendNumber(number) {
      // Append the selected number to the current operand, unless it already contains a decimal point
      if (number === '.' && this.currentOperand.includes('.')) return
      this.currentOperand = this.currentOperand.toString() + number.toString()
    }

    chooseOperation(operation) {
      // Choose the operation to be performed
      if (this.currentOperand === '') return // If there is no current operand, return
      if (this.previousOperand !== '') {
        this.compute() // If there is a previous operand, compute the result
      }
      this.operation = operation // set the operation
      this.previousOperand = this.currentOperand // Set the previous operand to the current operand
      this.currentOperand = '' // Clear the current operand
    }

    compute() {
      // Perform the computation based on the chosen operation
      let computation
      const prev = parseFloat(this.previousOperand)
      const current = parseFloat(this.currentOperand)
      if (isNaN(prev) || isNaN(current)) return // If either operand is not a number, return
      switch (this.operation) {
        case '+':
          computation = prev + current
          break
        case '-':
          computation = prev - current
          break
        case '*':
          computation = prev * current
          break
        case '÷':
          computation = prev / current
          break
        default:
          return
      }
      this.currentOperand = computation // Set the current operand to the computed value
      this.operation = undefined // Reset the operation
      this.previousOperand = '' // Clear the previous operand
    }

    getDisplayNumber(number) {
       // Format the number to be displayed on the calculator screen
      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() {
      // Update the calculator screen with the current and previous operands
      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()
  })