kenvantruong
5/29/2018 - 6:16 AM

Loan Calculator

Loan Calculator

a_Loan-Calculator.html
content_copyfile_download
<!doctype html>
<html lang="en">

<head>
  <title>Hello, world!</title>
  <!-- Required meta tags -->
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

  <!-- Bootstrap CSS -->
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/css/bootstrap.min.css" integrity="sha384-PsH8R72JQ3SOdhVi3uxftmaW6Vc51MKb0q5P2rRUpPvrszuE4W1povHYgTpBfshb"
    crossorigin="anonymous">
</head>

<style>
  #loading,
  #results {
    display: none;
  }
</style>

<body class="bg-dark">
  <div class="container">
    <div class="row">
      <div class="col-md-6 mx-auto">
        <div class="card card-body text-center mt-5">
          <h1 class="heading display-5 pb-3">Loan Calculator</h1>
          <form id="loan-form">
            <div class="form-group">
              <div class="input-group">
                <span class="input-group-addon">$</span>
                <input type="number" class="form-control" id="amount" placeholder="Loan Amount">
              </div>
            </div>
            <div class="form-group">
              <div class="input-group">
                <span class="input-group-addon">%</span>
                <input type="number" class="form-control" id="interest" placeholder="Interest">
              </div>
            </div>
            <div class="form-group">
              <input type="number" class="form-control" id="years" placeholder="Years To Repay">
            </div>
            <div class="form-group">
              <input type="submit" value="Calculate" class="btn btn-dark btn-block">
            </div>
          </form>
          <!-- LOADER -->
          <div id="loading">
            <img src="img/loading.gif" alt="">
          </div>
          <!-- RESULTS -->
          <div id="results" class="pt-4">
            <h5>Results</h5>
            <div class="form-group">
              <div class="input-group">
                <span class="input-group-addon">Monthly Payment</span>
                <input type="number" class="form-control" id="monthly-payment" disabled>
              </div>
            </div>

            <div class="form-group">
              <div class="input-group">
                <span class="input-group-addon">Total Payment</span>
                <input type="number" class="form-control" id="total-payment" disabled>
              </div>
            </div>

            <div class="form-group">
              <div class="input-group">
                <span class="input-group-addon">Total Interest</span>
                <input type="number" class="form-control" id="total-interest" disabled>
              </div>
            </div>
          </div>
        </div>
      </div>
    </div>
  </div>

  <!-- Optional JavaScript -->
  <!-- jQuery first, then Popper.js, then Bootstrap JS -->
  <script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN"
    crossorigin="anonymous"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.3/umd/popper.min.js" integrity="sha384-vFJXuSJphROIrBnz7yo7oB41mKfc8JzQZiCq4NCceLEaO4IHwicKwpJf9c9IpFgh"
    crossorigin="anonymous"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/js/bootstrap.min.js" integrity="sha384-alpBpkh1PFOepccYVYDB4do5UnbKysX5WZXm3XxPqe5iKTfUKjNkCk9SaVuEZflJ"
    crossorigin="anonymous"></script>
  <script src="app.js"></script>
</body>

</html>
app.js
content_copyfile_download
// Listen for Submit Button Cliked 
document.querySelector('#loan-form').addEventListener('submit', function (e) {

  // Hide results
  document.getElementById('results').style.display = 'none';

  // Show Loader
  document.getElementById('loading').style.display = 'block';

  setTimeout(calculateResults, 1500);

  e.preventDefault();
});

// Calculate Results Button Clicked
function calculateResults(e) {
  console.log('Calculating...');

  // Loan Amount & Interest Input
  const amount = document.getElementById('amount');
  const interest = document.getElementById('interest');
  const years = document.getElementById('years');
  const monthlyPayment = document.getElementById('monthly-payment');
  const totalPayment = document.getElementById('total-payment');
  const totalInterest = document.getElementById('total-interest');

  // Turn the Amount Input field into a Decimal
  const principal = parseFloat(amount.value);
  const calculatedInterest = parseFloat(interest.value) / 100 / 12;
  const calculatedPayments = parseFloat(years.value) * 12;

  // Compute monthly Payment
  const x = Math.pow(1 + calculatedInterest, calculatedPayments);
  const monthly = (principal * x * calculatedInterest) / (x - 1);


  if (isFinite(monthly)) {
    monthlyPayment.value = monthly.toFixed(2);
    totalPayment.value = (monthly * calculatedPayments).toFixed();
    totalInterest.value = ((monthly * calculatedPayments) - principal.toFixed(2));
    totalInterest.value = ((monthly * calculatedPayments) - principal.toFixed(2));

    // Show results
    document.getElementById('results').style.display = 'block';

    // Hide Loader
    document.getElementById('loading').style.display = 'none';
    //
  } else {
    showError('Please Check Your Numbers');
  }

  e.preventDefault();
}

// Show Error
function showError(error) {
  // Hide results
  document.getElementById('results').style.display = 'none';

  // Hide Loader
  document.getElementById('loading').style.display = 'none';



  // Create A Div
  const errorDiv = document.createElement('div');

  // Get Elements
  const card = document.querySelector('.card');
  const heading = document.querySelector('.heading');

  // Add Class
  errorDiv.className = 'alert alert-danger';

  // Create text node and append to div
  errorDiv.appendChild(document.createTextNode(error));

  // Insert Error Above Heading
  card.insertBefore(errorDiv, heading);

  // Clear Error after 3 seconds
  setTimeout(clearError, 3000);

}

// Clear Error
function clearError() {
  document.querySelector('.alert').remove();
}