script.js

// Initialize an empty string to store the user input
let inputString = ''

// Select the input field
const inputField = document.querySelector('input')
const resultDisplay = document.querySelector('#results')
const operators = ['+', '-', '*', '/']

// Select all the calculator buttons on the page
const calculatorButtons = document.querySelectorAll('button')

// Select the body element
const bodyElement = document.body

const parentBox = document.querySelector('.parent')

function generateRandomGradient () {
  // Generate random colors
  const color1 = getRandomColor()
  const color2 = getRandomColor()

  // Generate a random angle between 0 and 360 degrees
  const angle = Math.floor(Math.random() * 360)

  // Create the linear gradient string
  const gradient = `linear-gradient(${angle}deg, ${color1}, ${color2})`

  // return the generated linear gradient
  return gradient
}

function getRandomColor () {
  // Generate a random hexadecimal color code
  const letters = '0123456789ABCDEF'
  let color = '#'
  for (let i = 0; i < 6; i++) {
    color += letters[Math.floor(Math.random() * 16)]
  }
  color += '80' // so that the background is not a solid color
  return color
}

// Function to change the background color
function changeBackgroundColor () {
  bodyElement.style.background = generateRandomGradient()
  parentBox.classList.add('box-highlight')

  // Add a button press effect to the parent container
  setTimeout(() => {
    parentBox.classList.remove('box-highlight')
  }, 200)
}

function animateValueChange (element, end, duration) {
  const startValue = parseFloat(element.value) || 0 // Start from the current value
  const startOpacity = 0 // Start from opacity 0
  let startTimestamp = null

  const step = (timestamp) => {
    if (!startTimestamp) startTimestamp = timestamp
    const progress = Math.min((timestamp - startTimestamp) / duration, 1)

    const interpolatedOpacity = progress

    // Update the value and opacity (don't change anything other than alpha though, get the elements r, g, and b)
    element.value = end
    // Get R G and B of the text
    const rgb = window.getComputedStyle(element).color.match(/\d+/g)
    const r = rgb[0]
    const g = rgb[1]
    const b = rgb[2]
    element.style.color = `rgba(${r}, ${g}, ${b}, ${interpolatedOpacity})`

    if (progress < 1) {
      window.requestAnimationFrame(step)
    }
  }

  window.requestAnimationFrame(step)
}

// It is the  Function to change theme
function changeTheme (theme) {
  // It will remove existing theme classes from the body
  document.body.classList.remove('dark-theme', 'light-theme')

  // It will add the selected theme class to the body
  if (theme === 'dark') {
    document.body.classList.add('dark-theme')
  } else if (theme === 'light') {
    document.body.classList.add('light-theme')
  }
}

// Function to calculate and display the result
function calculateResult () {
  const inputValue = inputField.value
  try {
    // Replace percentage symbol (%) with '/100' before evaluation
    inputString = inputValue.replace(/%/g, '/100')
    // Replace √(first digit group) with 'Math.sqrt()' function for that digit group before evaluation
    inputString = inputValue.replace(/√([+-]*\d+)/g, 'Math.sqrt($1)')

    // Evaluate the user input as a mathematical expression using eval
    const result = eval(inputString)

    // Display the result in the second input field
    animateValueChange(resultDisplay, result, 500)

    // Revert back the Math.sqrt() function
    inputString = inputValue.replace(/Math.sqrt\((\d+)\)/g, '√$1')

    // Change the background color here
    changeBackgroundColor()
  } catch (error) {
    // Handle invalid expressions
    navigator.vibrate(200)
    inputField.value = ''
    inputString = ''
    resultDisplay.value = error.message // Clear the dashboard on error
  }
}

// Function to continuously update the result as the user types or presses buttons
function updateResult () {
  inputString = inputField.value

  try {
    // Check if the inputString is not empty and contains a valid expression
    if (inputString) {
      const result = eval(inputString)
      animateValueChange(resultDisplay, result, 500)
    } else {
      resultDisplay.value = '' // Clear the dashboard if the input is empty
    }
  } catch (error) {
    resultDisplay.value = '' // Clear the dashboard on error
  }
}

// Add an event listener to each button
calculatorButtons.forEach((button) => {
  button.addEventListener('click', () => {
    const buttonValue = button.textContent

    switch (buttonValue) {
      case '=':
        // Check if the inputString is not empty and contains a valid expression
        if (inputString) {
          calculateResult()
        }
        break
      case 'C':
        // Clear the inputString and reset the input field
        inputString = ''
        inputField.value = inputString
        // claer the Display field
        resultDisplay.value = ''
        break
      case 'M+':
        // Add the current input value to the memory value
        memoryValue += parseFloat(inputField.value) || 0
        inputString = ''
        break
      case 'M-':
        // Subtract the current input value from the memory value
        memoryValue -= parseFloat(inputField.value) || 0
        inputString = ''
        break
      case 'sin':
        inputField.value = Math.sin(parseFloat(inputField.value))
        inputString = inputField.value.toString()
        break
      case 'cos':
        inputField.value = Math.cos(parseFloat(inputField.value))
        inputString = inputField.value.toString()
        break
      case 'tan':
        inputField.value = Math.tan(parseFloat(inputField.value))
        inputString = inputField.value.toString()
        break
      case '^':
        const num = parseFloat(inputField.value)
        const result = num * num
        // inputString = result.toString();
        break
      case '√':
        // inputField.value = Math.sqrt(parseFloat(inputField.value));

        // Check if input field value is empty and if it is, not then √ should precede *
        const inputFieldValueLength = inputField.value.length
        if (inputFieldValueLength != 0 && !operators.includes(inputField.value[inputFieldValueLength - 1])) { inputField.value += '*' }
        inputField.value += '√'
        inputString = inputField.value.toString()

        break
      case 'log':
        inputField.value = Math.log(parseFloat(inputField.value))
        inputString = inputField.value.toString()
        break
      case 'π':
        inputField.value += Math.PI.toFixed(3)
        inputString = inputField.value.toString()
        updateResult()
        break
      case 'e':
        inputField.value = Math.E
        inputString = inputField.value.toString()
        break
      case 'X!':
        const numX = parseFloat(inputField.value)
        let factorial = 1
        for (let i = 1; i <= numX; i++) {
          factorial *= i
        }
        inputString = factorial.toString()
        break
      case 'CE':
        inputField.value = inputField.value.slice(0, -1)
        inputString = inputField.value
        break
      default:
        // Append the clicked button's value to the input field
        inputString += buttonValue
        inputField.value = inputString
        updateResult() // Update the result as you add operators
        break
    }
  })
})
inputField.addEventListener('input', updateResult)

// Set the date we're counting down to
const countDownDate = new Date('Oct 31, 2023 23:59:59').getTime()

// Update the count down every 1 second
var x = setInterval(function () {
  // Get today's date and time
  const now = new Date().getTime()

  // Find the distance between now and the count down date
  const distance = countDownDate - now

  // Time calculations for days, hours, minutes and seconds
  const days = Math.floor(distance / (1000 * 60 * 60 * 24))
  const hours = Math.floor((distance % (1000 * 60 * 60 * 24)) / (1000 * 60 * 60))
  const minutes = Math.floor((distance % (1000 * 60 * 60)) / (1000 * 60))
  const seconds = Math.floor((distance % (1000 * 60)) / 1000)

  // Display the result in the element with id="demo"
  document.getElementById('timer-text').innerHTML = 'Ends in ' + days + 'd ' + hours + 'h ' +
  minutes + 'm ' + (seconds < 10 ? '0' : '') + seconds + 's '

  // If the count down is finished, write some text
  if (distance < 0) {
    clearInterval(x)
    document.getElementById('timer-text').innerHTML = 'ENDED'
  }
}, 1000)